94

Orthopaedics and Traumatology

4 (19951, 94-105 (No 2), © Urban &V~gel, Munich

Proximal Tibial Osteotomy in Varusgonarthritis -

Modified Maquet Technique

Piet de Boer, Ulrich Boenisch

York District Hospital, Department of Traumatology and Orthopaedics, York, England

Surgical Principles

In varus osteoarthritis of the knee the force of weight bearing, which normally passes through the centre of the weight bearing surfaces, is medially displaced [4, 8].

In order to redistribute the load evenly over a larger articular surface a modified Maquet upper tibial osteotomy via midline vertical incision is performed. By valgus overcorrection of 5 °, the tibiai plateau is tilted and this changes the mechanical axis in such a way, that the resultant forces pass through the centre of the knee joint and at a right angle to the plane tangential to the articular surfaces [7, 9].

The degree of correction (varus deformity + 5 °) is determined preoperatively on the basis of a full length, single stance weight bearing film (120 cm x 30 cm, distance at least 3 m) [8].

The fibula is divided to allow adequate correction of the tibia; this is done by excising a segment of the fi- bula. Because of variations in the innervation of the extensor hailucis longus muscle this should be per- formed in a relatively safe area, about 160 mm distal to the fibular head [5] through a postero-lateral ap- proach [4]. The size of the excised segment depends on the degree of correction required.

A dome osteotomy (barrel vault osteotomy) above the level of the tibial tubercle allows a correction of up to 25 ° .

The osteotomy is compressed with at least four staples in two different planes.

Contrary to the technique described by Maquet [8] the distal tibial fragment is not advanced anteriorly.

Advantages

Allows precise correction of deformity.

Permits to modify angular correction during surgery.

A large contact area of cancellous bone reduces the risk of nonunion.

An osteotomy above the tibial tubercle allows the ex- tensor mechanism to compress the osteotomy. Be-

sides, the osteotomy is very close to the site of defor- mity.

The use of staples in two different planes allows early mobilisation and early weight bearing.

The method is simple and does not endanger the common peroneal nerve.

Prolonged plaster immobilisation is unnecessary.

Pier de Boer. L'lrich B,~emsch: Proximal Tibial Oqeotomy in Varusgonarthrilis Modified Maquet Technique

Or thop Tra umatol. 4 ( I qO'g ). 94-105 ( N~ 2 ) 95

Early passive and active knee movements are pos- sible.

D i s a d v a n t a g e s

A second incision for fibular osteotomy is necessary.

There is a risk of palsy of extensor hallucis longus muscle.

I n d i c a t i o n s

Evidence of osteoarthritic changes (primary OA, haemophilic arthropathy, posttraumatic OA) of the medial compartment with arthroscopically verified intact lateral compartment.

Disabling knee pain [3].

Post medial meniscectomy pain with evidence of ear- ly joint degeneration.

C o n t r a i n d i c a t i o n s

Valgus deformity except when due to malunion of upper tibial fracture.

Flexion contracture greater than 10 ° and limitation of flexion beyond 90 ° .

Bone loss with medial compartment with depres- sion of subchondral bone of more than a few milli- meters.

Need for anticoagulation with low molecular weight Heparin.

Delayed union or nonunion, which requires further operative procedures.

Creation of iatrogenic tibial fracture.

Prolonged period of rehabilitation and of recovery of normal daily activity.

Need for walking aids for between 6 and 12 weeks.

Palsy of extensor hallucis longus muscle.

Pain at site of fibular osteotomy.

P r e o p e r a t i v e W o r k U p

Arthroscopy of affected knee to assess the lateral compartment: this should be done in a session prior to the actual osteotomy.

Long leg, weight bearing (single stance) A. E and lat- eral view (90 x 30 cm, 120 x 30 cm, distance at least 3 m).

Determination of varus deformity and desired angle of correction.

Preoperative drawing of planned osteotomy and cor- rection.

Routine work-up as for any major operation.

Instability secondary to previous trauma, surgery.

Bicompartmental involvement.

Poor vascular status.

Poor general health, which does not allow anaesthet- ics and postoperative physiotherapy.

Decompensated metabolic diseases.

Age > 65 years.

Osteoporosis.

P a t i e n t I n f o r m a t i o n

General risks: infection, thrombosis, emboli, nerve and vascular damage.

I n s t r u m e n t s a n d I m p l a n t s (Figures 1 and 2)

- Image intensifier. - Basic instrument set. -Os t eo tomy guide for barrel vault osteotomy, avail-

able in 2 sizes. - 2 Steinmann pins (6 mm diameter, with sharp tip). - 2 osteotomes (8 to 10 mm wide, 2 different thick-

nesses). - Bone staples. - Staple introducer. - Hohmann retractors. - Oscillating saw with 2 cm endcutting blade. - Power drill, 2 mm drill bit. - Curved periosteal elevator. - Maquet pin guide. - 2 Charnley compression clamps.

96 Pitt de Boer. l "lrich l'~l~enlsch:

Pr,~:zm,d ribzal ( )~lcllll~m'~ in Varus~tmarthritis Modified Maquel Technique ()rlhop Fr;mmalt l l 4 (1'~95). 94-105 (No 2)

-Plastic template (Dr. D. Child. York District Hos- pital) (Figure 2).

P o s i t i o n i n g

- Supine position with the leg fully extended. - A p p l y a well padded pneumatic tourniquet to the

proximal third of the thigh.

-Internally rotate the leg to facilitate the fibular osteotomy but ensure a neutral position for the tib- iaI osteotomy to allow accurate use of radiographic control.

Fig. 1

Fig. 1 Instruments and implants: l = osteotomy guide avail- able in 2 sizes: 2 = sharp ended 6 mm pins to be introduced in- to the tibia to determine angle of correction (see Figure 8); 3 = osteotomes, 8 mm wide, 2 different thicknesses; 4 = staple introducer: 5 = staples {step staples and regular bone sta- ples): 6 = curved periosteal elevator: 7 = Maquet pin guide: 8 = Charnley compression clamps.

J 25 °

15 ° . ~

Fig. 2 Plastic template {Child) to verify the angle of correc- tion. The template is superimposed on the image intensifier picture, after the Steinmann pins have been inserted at the desired angle, the degree of angulation can be read directly from the template and if necessary the angle between the pins (pin B) can be altered. Fig. 2

Pier de Boe r , [. 'lrich Bnenlsch: Proximal l ' ib ia l Ostc~m~my in V a n l s g o n a r t h r t t i s - Modif ied MaqucI l ' e c h m q u c

O r t h o p . T r a u m a t o l 4 ~ 1995). 94-[115/No 21 97

Surgical Technique Fig. 3 to 11

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Fig. 3a Fig. 3b

Fig. 4a and 4b Trace the outlines of the knee from the A. P. view of the loaded joint. Draw a line, A, parallel to the joint axis through the upper tibia, just below the joint surface. This represents the position of the first Steinmann pin. Draw a second line, B, distal to the tibial tubercle at an angle of "c~ + 5 °" to the first line B. This represents the position of the second Steinmann pin. Trace in the line of the barrel vault osteotomy, C, which lies proximal the insertion of the patella tendon onto the tibial tubercle (a). Now trace in the tibia below the osteotomy line on a second transparent sheet. Include the second Steinmann pin line, B. Rotate this tracing paper until line B and A are parallel. This composite diagram gives you the final operative appearance (b). Initially it is worth tracing out the entire tibia in its new position and then superimposing it on the original weight bearing film. If the correction has been well calculated a line drawn between the centre of the femoral head and the centre of the ankle will pass through the knee lateral to the tibial spines.

Fig. 3a and 3b Take a long leg, single leg weight bearing A. P. and lateral film of the entire lower limb (90 cm x 30 cm or 120 cm x 30 cm, 3 m distance). Ensure that the patient has his knee fully extended when the film is taken. The centre of the hip, the knee and the ankle normally lie on a straight line (a). Ensure that there is no external or internal rotat ion of the limb by checking the position of the patella on the film. External rotation of the limb will give an appearance of varus deformity. Internal rotation of the limb will give the impression of valgus deformity. Draw a line from the centre of the femoral head to the midpoint of the tibia at the level of the joint surface. Draw a second line between this point and the centre of the ankle joint. The angle c~ between these two lines is the measure of the degree of the deformity (b). Add 5 ° to this angle to give you valgus overcorrection. ~'a + 5 °" therefore represents the degree of correction that is required.

A .-....a

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Fig. 4a

A

B

ig4b

98

Pier de Boer, I 'lrich B()cnisch: Proximal T ib i a l Osteotomy m Varusgonarthritis - Modified Maquel I 'cchnique

Orthop F rauma lo l 4 fl995), 94-105 (No 2)

Fig. 5a to 5c Place the patient supine on the operat- ing table. Exsanguinate the limb and apply a high thigh tourniquet which is well padded. Internally ro- tate the limb by getting the assistant to internally rotate the foot. This will bring the posterolateral aspect of the fibula into view. Palpate the groove between the peroneal muscles anteriorly and the gastrocnemius-soleus muscles posteriorly. Make a 5 cm longitudinal straight incision over this groove about 160 mm distal to the fibular head (a). Divide the deep fascia in the line of the skin incision. Using blunt dissection folIow the lateral interosseous membrane in a medial direction to come down on- to the lateral aspect of the fibula. Insert a Hohmann retractor over the anterior aspect of the fibula and detach those muscle fibers arising from the bone at that point. Next insert a second Hohmann retrac- tor posteriorly to complete exposure of the bone (b and c).

Fig. 5a //i M. peroneu V brev. /

M. peroneus long. / / M. tibialis ant, t . / /

~ . ~ ~ M. ex tensor digit, l ong . / / i i \ -

M. soleus Fig. 5b M. gast rocnemius

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Fig. 5c

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Fig. 6 Divide the fibula obliquely using an oscillat- ing saw. It can be carried out safely in the region between the middle and distal thirds of the fibula, about t60 mm distal to the fibular head [5]. For cor- rection of 10 to 15 ° excise 5 mm of fibula. For cor- rection of 15 to 20 ° excise 8 mm of fibula. For correction of 20 to 25 ° excise 10 mm of fibula. In dividing the fibula you will almost certainly divide terminal branches of the peroneal artery and vein. For this reason close the wound over a suction drain. Close the fibula incision completely before commencing the tibial operation as this can only comfortably be done with the leg fully internally rotated.

Piel de Boer. 1 lrich Bocmsch Prllxlmal l'ihM ()ste¢~torn} in Varusgonarlhrilis - Modilied Maqud lcchniqu¢

()rthop Traumatn[. 4 (1995]. 94-It)5 (No. 21 99

~:\ / I . i .,,4"~ i! inf. med. I t \ : /~ ~ ';",V~' '/V. saphe, t t'J, . ; : magna

A. genus inf. lat. J /

N. peronaeus " i i ' K ~ " / [ ~ ! /

N N. peronaeus superfic."

M tibialis ant."

Fig. 7 Make a longitudinal incision in the mid- line, centred on the tibial tubercle. The length of the incision depends on the width of the leg. En- sure that the incision is of sufficient length to al- low retraction of the skin flaps without tension. Incise the fascia on either side of the patellar ligament. Take care at that time to coagulate ter- minal branches of both the inferior medial and inferior lateral geniculate arteries. Using a sub- periosteal technique expose the upper medial as- pect of the tibia at the level of the tibial tubercle with the curved periosteal elevator. Use a simi- lar technique laterally, detaching part of the ori- gin of the tibialis anterior muscle. Insert Hoh- mann retractors on either side of the bone.

Fig. 8 Insert the first 6 mm Steinmann pin under image intensifier control from lateral to medial via a stab incision, using a power drill. Ensure that the pin is parallel to the joint surface and as close to it as possible (A). Next insert the second Steinmann pin some 10 cm be- low the level of the osteotomy (B). This pin should be inserted at the preoperatively calculated angle ("cC + 5 °) to the first pin, using the Maquet pin guide. Take a radiograph at this time to ensure the proper angle of planned correction. This can be easily done using the image on the image intensifier and superimposing the plastic template. If the preoperatively calculated angle is not achieved, the position of pin B must be corrected.

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Proximal Tibial Osteotomy in Varusgonarthritis - Modified Maquet Technique Orthop. Traumatol. 4 (1995), 94-105 (N~ 2)

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Fig. 9 Fig 10

Fig. 9 Apply the osteotomy guide to the anterior surface of the tibia just above the insertion of the patellar ligament into the tibial tubercle. Two sizes are available, the larger one usually used. Drill a series of 2 mm drill holes until the tip of the drill bit touches the posterior cortex but do not penetrate it. In doing so a series of holes in the shape of a dome will be created.

Fig, 10 Connect these drill holes using a 8 to 10 mm wide osteotome. Divide the bone down to the posterior cortex without pene- trating it. Next insert an osteotome of same width, but of greater thickness. This will hold the osteotomy surfaces apart. Now place the thinner osteotome again in the osteotomy site and carefully divide the posterior cortex. Repeat this two-osteotome technique until the osteotomy is complete. The thick osteotome will stop the thin osteotome from getting squeezed between the bony surfaces and therefore it can be advanced under perfect control. An osteotome that rapidly penetrates the posterior cortex could damage the vascular structures that lie immediately posterior to the osteotomy. A useful technique is to listen to the sound of the osteo- tome. An intact cortex has a high pitch, ringing sound. As soon as the sound changes the osteotomy has been completed. When the osteotomy is complete apply a valgus force to the limb. There is normally an audible crack heard at this moment , representing the final completion of the osteotomy.

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Fig. 11 Abduct the distal fragment until both Steinmann pins are parallel. Apply 2 Charnley compression clamps to the Stein- mann pins. Apply compression to the osteotomy using these clamps, ensuring that the pins remain parallel. Check the posi- tion of the pins on the image intensifier. Now insert staples across the compressed osteotomy site. You will need to use step staples on the lateral side. Ensure that your staples are inserted in different planes. If all staples are inserted in the A. P. plane, then the osteotomy may be unstable in the frontal plane and you will get windshield wiper effect. Take a final radiograph to ensure that none of the staples have inadvertently penetrated the knee joint. Remove the compression clamps. Remove the Steinmann pins. Check the knee under image intensification to ensure that the osteotomy is stable in flexion. Apply valgus and varus forces to the osteotomy to check that you have achieved stable conditions. Close the wound over a suction drain. Apply a compression wool and crepe bandage.

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Postoperative Management

E n c o u r a g e isometric quadr iceps exercises as soon as

possible. R e m o v e the drain at 48 hours pos tope ra -

tively and check the wounds. If the wounds are satis- factory and there is no h a e m a t o m a fo rmat ion then

c o m m e n c e active and passive flexion of the knee up to 70 ° . R e m o v e the sutures at ten days pos topera t ive - ly and apply a long leg cyl inder plaster. Mobilise the

patient , partial weight bear ing (20 kg is permit ted) .

R e m o v e the plaster six weeks after surgery and take

a radiograph. If this is sat isfactory then full weight bear ing is al lowed. R e p e a t the r ad iograph at three

months . Six months pos topera t ive ly repea t the long leg weight bear ing film to check the axial a l ignment .

We rout inely follow our pat ients up year ly with ra- d iographic control but this is largely for research,

ra ther than clinical considerat ions .

102

Pict de B~cr. [ I n c h Bocnlsch: Proxinml Tibml ( ) q e o m m ~ m Varusaonarthritis - Modified Maquct gcchmque

Orthop Traumaml. 4 119951. t)4-1II5 (No. 2)

Special Surgical Considerations

We do not recommend anterior displacement of the f inal tubercle as originally described by Maquet [8]. Anterior displacement reduces the area of bone contact, decreasing the stability of the osteotomy and increasing the risk of delayed or nonunion. Anterior displacement makes the use of staples very difficult. It reduces compression forces across the patello- femoral joint and is rarely needed in varus gonarthri- tis.

The use of staples instead of the prolonged use of Charnley clamps allows early movement of the knee.

Staples avoid the risk of sepsis that occurs when- ever pins are left in bone for a long period of time.

Intra- and Postoperative Complications

Compartment syndrome: has been described follow- ing this procedure. The commonest source of bleed- ing is from the inferior geniculate arteries and these must be coagulated during surgery. Suction drains must be used and the patients must be carefully mo- nitored for the first 24 hours following surgery. In case of compartment syndrome, a fasciotomy must be performed immediately.

Paralysis of the extensor hallucis longus muscle: al- though anatomy books generally would suggest that the extensor hallucis longus gets its nerve supply at the level of the proximal third of the fibula, in a small percentage the nerve supply occurs more distally. Even if you approach the fibula by coming along the lateral intramuscular septum you may create a trac- tion lesion to this muscle. In our series this compli- cation has been 6%, most of which recovered. We therefore recommend to do the fibular osteotomy about 160 mm distal to the fibular head [5]. If the paralysis persists for more than nine months, a recov- ery can not be expected.

Sepsis: is a major complication as in all internal fixa- tions. We recommend the use of intraoperative anti- biotics and intraoperative irrigation with antiseptic solutions. We also recommend postoperative anti- biotics for a period of 48 hours until the drains have been removed as well as the use of linen outer gloves to minimalise perforation of rubber gloves during surgery.

Pain (30 Points) no pain at any time 30

no pain on walking 15

mild pain on walking 10

moderate pain on walking 5

severe pain on walking 0

no pain at rest 15

mild pain at rest 10 moderate pain at rest 5

severe pain at rest 0

Function (22 Points) walking and standing unlimited 12

walking distance of 5-10 blocks and standing ability intermittent (< 1/2 h) 10

walking distance of 1-5 blocks and standing ability up to 1/2 h 8

walking less than 1 block 4

cannot walk 0 climbing stairs 5 climbing stairs with support 2

transfer activity 5 transfer activity with support 2

Range of Motion (18 points) 1 point for each 8 ° of arc of motion 18 to a maximum of t8 points

Muscle Strength (10 points) excellent, cannot break the quadriceps power 10 good, can break the quadriceps power 8

fair, moves through the arc of motion 4 poor, cannot move through the arc of motion 0

Flexion Deformity (10 points) no deformity 10 less than 5 ° 8

5-10 ° 5

more than 10 ° 0

Instability (10 Points) none 10 mild, 0-5 ° 8

moderate, 5-15 ° 5

severe, more than 15 ° 0

Subtraction one cane 1

one crutch 2 two crutches 3

extension lag of 5 ° 2

extension lag of 10 ° 3

extension lag of 15 ° 5 each 5 ° of varus 1

each 5 ° of valgus 1

Tabelle 1. HSS-Score according to Insall.

Pier de Boer. Ulrich B{lenlsch: Pr~xtma{ FihlaL ( stcotomy in Varusgonarthritis - Modified Maquel Tcchmque

Or thop Traumato l 4 (19t)5), 94-i(15 (No 2) 1 0 3

Total Age Follow-up period in years Follow-up criteria Number

De Boer and Boenisch 71 (104) 31-70 2-12 (7.2) (1993)

Results: 26 (36.6%) 33 (46.4%)

7 (9.8%) 5 (7.2%)

29 (41%) 19 (27%)

17 (24%)

6 (8%)

excellent good fair poor

no pain minimal pain after heavy labour minimal pain after light labour much pain

HSS/Insall

Patients' outcome

Table 2. Long term results following Maquet tibial osteotomy.

In the presence of infection the wound should be de- brided and irrigated. The choice of antibiotics de- pends on the culture and sensitivity study.

Errors and Potential Hazards

Dividing the posterior cortex of the proximal tibia is a potentially hazardous procedure due to the close proximity of the popliteal ar tery and its branches. Overpenetra t ion of the cortex with an osteotome is to be avoided. We therefore stress the use of the two osteotome technique to prevent the cutting osteotome from suddenly moving forward. You must check the vascular supply to the foot following sur- gery and if there is any doubt perform an arterio- gram. We did not have vascular complications in our series.

Results

Between 1976 and 1991 71 proximal tibial osteoto- mies were performed on 65 patients. The average age of the patients was 51 years (31 to 70). The male to female ratio was 4 : 1. The average follow-up was 7 years (2 to 12).

Postoperative assessments were made using a stan- dardised knee score (Insall HSS score). 41% of the patients reported no pain on any physical activity. 27% of the patients reported pain on physical activi-

ty but no limitation of function, 24% of the patients had pain on physical activity which limited their func- tion. 8% of the patients reported severe pain. Two of these patients required total knee replacement. These patients had knee replacement on an average of 3.5 years postoperatively.

Walking distance was unlimited in 68% of the pa- tients. 32% could not walk more than 1 mile.

There was no difference in the pre- and postopera- tive range of movement in the knee.

Since 1984 all patients have had yearly long leg weight bearing radiographs. Of these 43 osteotomies 39 (90%) maintained the predicted degree of cor- rection to within 2 °. Four (10%) patients lost correc- tion. All these patients were female and over the age of 50. One patient went back into varus and requir- ed a total knee replacement. This patient was the oldest in the series and also the only case of delayed union.

Complications

There was one case of delayed union (> 6 months) but no case of nonunion. No reoperations were car- ried out.

There were two infections (2.8%). Both were super- ficial and both settled with antibiotics.

P!c: de Boer. I i n c h Boeiiisch: Proximal "ribml ()st~otomt m k arusgonarthntts - Modified Maquet Fechniquc

104 Orth,~p Traumaloi. 4 11995), 94-105 (No 21

Total Age Follow-up period Follow-up criteria Number in years

Maquet 41 (?) 48-80 1-8 (2.4) (1975) [9]

Results:

Maquet (1980) [81

Results:

Krempen (1982) [5]

Results:

Wohlfahrt (1991) [11]

Results:

Sundaram (1986) [10]

Results:

32 (78%) excellent 5 (12%) good 4 (10%) fair and poor

135 (?) ? 1-12 (7.3)

85 (63%) excellent 26 (19%) good

9 (7%) fair 15 (11%) poor

40 (?) ? 1-4.5 (2.5)

15 (37.5%) excellent 20 (50%) good

3 (7.5%) fair 2 (5%) poor

(299) ? 10-19 (11.9) 91

105

21 (23%) excellent 26 (29%) good 13 (14%) fair 31 (34%) poor

44 (48%) much better 20 (22%) better

8 (9%) same 19 (21%) worse

(140) 38-79 1-17 (4.8)

79 (75.2%) excellent/good 20 (19.1%) fair

6 (5.6%) poor

26 (24.8%) most satisfied 51 (48.6%) satisfied 17 (16.2%) not satisfied 11 (10.4%) no opinion

Maquet-Score

Maquet-Score

Maquet-Score

HSS/Insall

Patients' outcome

Aichroth Score

Patients' outcome

Table 3. Long term results of various authors following Maquet tibial osteotomy.

No peroneal nerve palsies were found, 4 patients (5.6%) had paralysis of the extensor haUucis longus muscle. 2 patients fully recovered and the other 2 on- ly partially.

Despite 2 deep vein thromboses (2.8%), there were no major complications like pulmonary emboli, myo- cardial infarction or cerebrovascular problems. No

death occured intraoperatively or in the postopera- tive recovery and rehabilitation period.

References

1. Aichroth, P.: A knee function assessment chart. J. Bone Jt Surg. 60-B (1978), 308-309.

Pitt de Boer. Ulrich Boenisch: Proximal Tibial Osteotomy in Varusgonarthritis - Modified Maquet rechntque

Orthop. Traumatol. 4 (1995), 94-105 (No. 21 105

2. Blauth, W., B. Sttinitz, J. Hassenpflug: Die interliga- ment~ire valgisierende Tibiakopfosteotomie bei Va- rusgonarthrose. Operat. Orthop. Traumatol. 5 (1993), 1-15.

3. Crenshaw, A. H.: Campbell's operative orthopaedics, 8th ed. Mosby, St. Louis 1991, p. 1020-1028.

4. Hoppenfeld, S., P. de Boer: Surgical exposures in or- thopaedics, the anatomical approach. J. B. Lippincott Comp., Philadelphia 1984.

5. Kirgis, A., S. Albrecht: Palsy of the deep peroneal nerve after proximal tibial osteotomy. J. Bone Jt Surg. 74-A (1992), 1180-1185.

6. Kremperi, J. F.: Experiences with the Maquet barrel vault osteotomy. Clin. Orthop. rel. Res. 168 (1982), 86-96.

7. Kummer, B.: Biomechanische Grundlagen beanspru- chungsfindernder Osteotomien im Bereich des Knie- gelenks. Z. Orthop. 19 (1977), 923 ft.

8. Maquet, P.: Valgus osteotomy for osteoarthritis of the knee. Clin. Orthop. rel. Res. 120 (1975), 143-148.

9. Maquet, P.: The biomechanics of the knee and surgi- cal possibilities of healing osteoarthritic knee joints. Clin. Orthop. rel. Res. 146 (1980), 102-109.

i0. Maquet, P.: Biomechanics of the knee, 2nd ed. Sprin- ger, Berlin - Heidelberg - New York 1984, p. 165 ff.

11. Sundaram, N. A.: Dome osteotomy of the tibia for osteoarthritis of the knee. J. Bone Jt Surg. 68-B (1986), 782-786.

12. Wohlfahrt, A.: Die valgisierende Tibiakopfpendel- osteotomie. Z. Orthop. Grenzgeb. 129 (1991), 72-79.

Key Words Varus gonarthritis • High tibial osteotomy • Maquet bar- rel vault osteotomy

Address all correspondence to: Mr. Piet de Boer Consultant Orthopaedic Surgeon York District Hospital Wigginton Road York Y03 7HE England