denim et al. (1998) - a radiographic evaluation of oblique closing base wedge osteotomies for the...

7/27/2019 Denim et al. (1998) - A radiographic evaluation of oblique closing base wedge osteotomies for the correction of h

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The Foot (1998) 8, 33-370 1998 Harcourt Brace &Co. Ltd

ORIGINAL ARTICLE

A radiographic evaluation of oblique closing base wedgeosteotomies for the correction of hallux abductus valgusF. Denim, S. Rees, M. TagoeThe Hillingdon Hospital, Middlesex, UKSUMMARIC The radiographs of 21 patients who underwent oblique closing base wedge osteotomies (OCBWO)were evaluated to determine the degree of intermetatarsal (IM) angle reduction, first metatarsal position andlength. All the procedures were performed using association for osteosynthesis rigid internal fixation, lagtechnique and hinge axis principles. Al l patients were immobilized post-operatively for 6 weeks in a below-kneecast (non-weightbearing). The results showed a mean reduction in the IM angle of 8.9 (SD f 2.3) whichwas highly significant (P < 0.001). The mean decrease in the metatarsal declination angle (dorsif lexion) was 0.4(SD f 3.08). This was less than the threshold for clinica lly significant metatarsal elevatus (5). The first metatarsalwas shortened on average by 1.76 mm (SD f 0.98) which is within the safety net of 3-4 mm, above which isassociated with complications. This study indicates that the OCBWO can be an effective, predictable and stableprocedure for reducing appropriate hallux valgus deformities without clinically significant elevatus orshortening.

INTRODUCTIONThe purpose of this study was to assess he incidenceof clinically significant iatrogenic elevatus andmetatarsal shortening following the long oblique clos-ing base wedge osteotomy (OCBWO) with screw fixa-tion. Basal osteotomies allow for the correction oflarge intermetatarsal (IM) angles which are beyondthe scope of the traditional distal procedures. Thetechnique became popular in the 1960s and 1970sprior to the widespread recognition of associatedcomplications. The original transverse base wedgeosteotomy (BWO) was inherently stable, due to theperpendicular relationship of opposing bone surfacesto the long axis of the metatarsal. This resisted tele-scoping and shortening of the fragments. However,the disadvantage was the limited scope for fixation,either two crossed K-wires or horizontal wire loops.This did not provide adequate stabil ity and increasedthe probability of complications such as firstmetatarsal shortening and elevation, delayed and nonunions. This problem was subsequently addressed bythe OCBWO, which allows for rigid internal screwfixation, decreasing the likelihood of complicationsz4Since the introduction of the A0 technique and thehinge axis concept, the OCBWO has once again seenan increase in popularity.

Correspondence to M. Tagoe, Consultant Podiatrist, TheHillingd on Hospital, Pield Heath Road, Uxbridge, Middlesex, UK.

However, some studies stil l indicate a high inci -dence of iatrogenic complications associated with thisprocedure, Haendel and LindholmS stated that eleva-tus was almost universal following 59 base wedgeosteotomies. Despite this, the base wedge osteotomyis sti ll advocated when the intermetatarsal angle ishigh,6-8 because distal osteotomies are unable toreduce these deformities sufficient ly. A failure toaccomplish sufficient IM angle correction would seri-ously compromise the surgical outcome.9 This couldleave the surgeon with a quandary; inadequate IMangle reduction for hallux valgus is likely to result in apoor outcome, but alternatively basal osteotomies arelikely to precipitate hallux limitus or metatarsalgia.

PATHOMECHANICSElevated first metatarsalThe first metatarsal phalangeal joint rotates primarilyaround a vertical axis. The joint is described as beingginglymoarthrodial. During plantar flexion and thefirst 20-30 of dorsiflexion the joint works in a hinge-like capacity (ginglymus). Root et al postulated thatduring normal gait, approximately 65-75 of dorsi-flexion is required at the first metatarsal phalangealjoint. For this to occur the first metatarsal mustplantarflex on the base of a stable proximal phalanxduring the propulsive period of gait, enabling theextended range of motion. Failure of this mechanism

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34 The Foot

can produce jamming of the joint and subsequentdegenerative joint disease. A dorsiflexed first ray(either congenital or acquired) is considered to be amajor component in the pathogenesis of halluxlimitus or rigidus. An iatrogenically elevated firstmetatarsal is therefore to be avoided at all costs. Astudy by Carrel and Sokoloff,6 indicated that a 5metatarsal elevation would have a clinically signifi-cant impact.

Firs t metatarsal lengthThe relative length of the first metatarsal is alsoimportant in the function of the first ray during gait.The normal metatarsal parabola should exhibit firstand third metatarsal heads of approximately equallength and a longer second metatarsal. This formulaallows the first metatarsal to plantarflex on the baseof a stable proximal phalanx, while the secondmetatarsal head momentarily supports the additionalforce. This process enables the extended range ofmotion at the first metatarsal phalangeal joint tooccur, which is necessary during normal gait. If thefirst metatarsal is excessively short then the amount ofplantarflexion needed for it to remain a weightbear-ing column increases. At a certain point its abili ty tofunction in this capacity is reduced and the body-weight is transferred lateral ly to the lesser metatarsals.This can lead to non-specific aching (metatarsalgia),callous and plantar digital neuritis, etc. Carr andBoyd12 postulated that an iatrogenic shortening ofmore than 34 mm caused a significant change in theforefoot loading patterns.

Modification of the osteotomy from a transverseto an oblique form allows for rigid internal fixation.This combined with an intact cortical hinge angledto plantar flex the metatarsal head has reduced theaforementioned complications.

METHODOLOGYA 2-year retrospective study was conducted on 21patients utiliz ing pre- and post-operative radiographs.All the operations were performed at the HillingdonHospital, by Mr M. Tagoe, Consultant Podiatrist . A llthe patients were female with an average age of 36.5years (range 16-67 years) and were included on thebasis of an IM angle of 12 or above. Patients wereexcluded on the basis of inadequate follow-up, degen-erative joint changes, significant osteoporosis or non-compliance.The pre- and post-operative lateral and dorso-plantar weightbearing radiographs were compared bymeasuring the IM angle, metatarsal elevatiomdeclina-tion angle and first metatarsal length using standardradiographic measurement techniques.13 All measure-ments were performed by the same person and thendouble checked by a third party.The Foot (1998) 8,33-37

Surgical technique (Figs 1 and 2)A dorsolinear incision is placed from the base of theproximal phalanx of the hallux extending to the firstmetatarsal cuneiform joint, lying medial to the exten-sor halluc is longus tendon. The wound is deepened bysharp dissection ensuring haemostasis. The lateralside of the metatarsal head is then exposed bydividing the tissue planes with a curved haemostatto perform a lateral capsulotomy and release of theabductor hallucis tendon. A dorsolinear capsular andperiosteal incision is made medial to the extensorhallucis longus tendon.

Fig. l--Preoperative hallux valgus.

Fig. 2-Postoperative obliqu e closing base wedge osteotomy.

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Correction of hallux abductus valgus 35The medial eminence is then removed flush with

the medial line of the shaft of the metatarsal using apower saw. Attention is then directed proximallywhere a single 0.045 Kirschner wire is placed throughthe bone 1 cm distal to the metatarsal cuneiformjoint. This acts as a guide in the angulation of theosteotomy cuts (hinge axis concept) and helps tomaintain an intact cortical hinge medially. The size ofthe wedge removed is dependent on the degree of lat-eral rotation of the first metatarsal needed to reducethe IM angle appropriately. This is assessed utiliz ingpre-operative weightbearing dorso plantar radio-graphs. For the less experienced surgeon, pre-opera-tive templates can be made to reduce the likelihood ofover or under correction.

The osteotomy is then closed down and if neces-sary the medial cortical hinge feathered to reducethe tension at the osteotomy site. The position istemporarily maintained with bone reduction for-ceps while fixation is achieved with either one3.5 mm cortical screw or two cortical screws(2.7 mm and 2 mm). In both instances this is carriedout in a lag screw fashion with standard A0 tech-nique. The wound is then closed in layers usingVicryl . A proximal Akin osteotomy was performedin conjunction to realign the hallux in threepatients. A post-operative dressing and a plasterof Paris below-knee cast, non-weightbearing isapplied. This is maintained for 3-5 days whereupona below-knee non-weightbearing Scotch cast isapplied for a further 5 weeks.Hinge axis conceptThe retention of an intact medial hinge allows thedistal metatarsal segment to rotate about thispivot. The hinge forms the axis of motion and thesecond point of fixation. The axis can be manipu-lated to provide the desired transverse plane motionof the distal metatarsal segment with or without asagittal plane component. The traditional axis ofbasal osteotomies had inherent problems becausethe osteotomy was perpendicular to the firstmetatarsal, resulting in elevation as well as lateralrotation (Fig. 3).

The reason for this lies in the normal anatomicaldeclination angle of the first metatarsal relative to theground. To counteract this, the osteotomy is alignedperpendicular to the ground, which exclusively allowsfor transverse plane motion. To provide plantar flex-ion of the metatarsal head the axis of the osteotomycan be offset in the frontal plane (dorsal lateral toplantar medial).Metatarsal shortening is inevitable with any basalosteotomy. 15,1b owever, the hinge axis concept cancompensate for the majority of the shortening byallowing plantar flexion of the distal metatarsal seg-ment in a predictable and controlled manner.14

0 1998 Harcourt Brace & Co. Ltd

Fig. 3-Shows the effect of orientating the osteotomyperpendicular to the ground as opposed to the metatarsal.Rotation with the axis perpendicular to the metatarsal wouldelevate the head, the axls bemg offset relative to the ground(dotted line). This is not the case when the axis 1s perpendicular tothe weightbearin g surface.

RESULTS AND DISCUSSIONThe OCBWO is specifical ly designed to address highIM angles which was effectively demonstrated by theresults in this study (Fig. 5). The mean IM anglereduction was 8.93 which was highly s tatistical lysignificant (P < 0.001, Table).

Traditionally, there have been concerns that basalosteotomies produce an iatrogenically elevated firstray. Schuberth et alI6 reported an elevatus incidence of93% following BWOs. The results of this study do notsupport this and demonstrate that using the protocolin this paper the problem of elevatus is far rarer thanprevious studies have indicated (14%, Fig. 6). A 5decrease in the declination angle (dorsiflexion) wasidentified as the point at which c lin ical ly significantcomplications can arise.5-6i6 The results from thisstudy show that in 11 cases (52%) the metatarsal dec-lination angle increased (the first metatarsal was plan-tar flexed). Eighty-six per-cent had changes below the

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36 The FootTable-Comparison of radiographlc angles

Preoperat ive Postoperat ive Correct ionIntermetatarsalangle (degrees)Metatarsal elevat ion/declinat ionangle (degrees)Metatarsal length (mm)

15.7 f 2.19 6.7k2.17(range 12-19) (range 3-11)11 k3.71 10.6 + 3.75(range 5-21) (range 5-17)6Oi:2 58i 1(range 58-62) (range 57-59)

8.9 + 2.30.4 f 3 081.8 f 0.98

OCBW O pre- and post-operat ive radiographic results. The radiographs were measured with a tractograph.All data is expressed as mean i SD, n = 21,

II fII

IM

I

L

Fig. &The axis is perpendicular to the ground in the sagit talplane (dotted line) but o ffset in the frontal plane (solid line). Thtsallows the metatarsal head to pivot towards the second metatarsaland plantar f lex.

IM angle (degrees) Metatarsal Metatarsaldeclination (degrees) length (mm)r------

Fig. 5-A comparison of mean pre- and postoperat ive angles.Preop IM angle 1.5 f 2.19, postop 6.7 f 2.17. Preop metatarsaldeclination angle 11 rt- 3.71, postop 10.6 I t -3.75. Preop metatarsallength 60 f 1.225, postop 58.19 k 0.6. All data expressedmean + SD, n = 21.

5 threshold, although a small percentage (14%)exceeded this cri tical point. The average increase inmetatarsal elevation in this study was 0.4 (SD +3.08), and there was not a statistically significantdifference between the pre- and postoperativemetatarsal position.

The significance of preserving the length of the firstmetatarsal was demonstrated by Carr and Boyd.lZThey noted that a shortening of more than 34 mmwas clinically significant, affecting a change in forefootloading patterns post-operatively, which resulted in anincreasing force being borne by the lesser metatarsals.The BWO is recognized to shorten the first metatarsaland this is confirmed by this study. The average degreeof shortening was 1.8 1 mm (Fig. 7) which is comfort-ably within the safe range of 34 mm and 76% hadless than 2 mm of shortening (Fig. 8). However, therewas a highly significant difference between the pre- andpostoperative values (P < 0.001). This i s the product ofthe minimal variation in the range of pre- and post-operative data. All the patients were female with mini-mal variation in metatarsal lengths (range 58-62 mm)and therefore the postoperative change was significantbecause it was unlikely to have occurred by chance.

CONCLUSIONThe long OCBWO with internal compression fixationvia the A0 cortical lag screw technique has, in ourexperience, been a consistently effective procedure.Success in minimizing the risk of metatarsus primuselevatus, excessive metatarsal shortening, delayed andnon unions was dependent on:0ii)

iii)

Proper angulation of the osteotomy axisenabling lateral rotation and plantar flexion.The oblique nature of the osteotomy whichallows for good interfragmental compression viathe A0 lag screw technique.Six weeks non-weightbearing, as the osteotomyis not sufficiently stable enough, to allow loadingof the first ray.

This paper demonstrates that clinica lly significantfirst metatarsal elevatus, shortening or delayed and

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Correction of hallux abductus valgus 37

A (52%)

B (34%)Fig. 6-Analysis of postoperative metatarsal position.Postoperative alterations m the metatarsal declinatio n angles. 52%(12 = 11) had an increased declinatio n angle (plantar flexed). 34%(n = 7) had a decreased declination angle < 5 14% (n = 3) had adecreased declination angle > 5. Key: A = increased declinatio nangle (plantar flexed): B = decreased declination angle < 5;C = decreased declination angle z 5.

non unions are unlikely complications provided theabove principles are adhered to. A further studydesigned to examine the post-operative clin ical andbiomechanical effects of the OCBWO is required.ACKNOWLEDGEMENTSThe authors wish to express their gratitude to Harrow andHillingd on Healthcare NHS Trust and Hilling don Hospital stafffor their kmd help in preparing this study.

REFERENCES1 Martm D E, Bhtch E L. Alternatives to the closing base

wedge osteotomy Clinics in Podiatric Medicine 1996; 13:515-531.

2. Ruth J, Banks A S. Proximal osteotomies of the firstmetatarsal in correction of hallux abduct0 valgus In:McGlamry E D (ed). Comprehensive textbook of footsurgery. Baltimore: Williams & Wilkins, 1987; 195-211.

3. Juvara E. LHallux valgus; son traitment operatoire. Rev-Chir1932; 5: 321

4. Gudas C. Compression screw fixation in proximal closmgbase wedge osteotomies for metatarsus pnmus varus: initialobservations. J Foot Surgery 1979; IS: 10.

5. Haende l C; Lindh olme J A First metatarsal base wedgeosteotomies. JAPA 1982; 72.550-556

6. Carrel J M, Sokoloff H M. Complications m Foot and AnkleSurgery (3rd Edition). Baltimore. Williams &Wilkins,American College of Foot Surgeons. 1992.

7. Lapidus P W. The authors bunion operation from 1 931-59.Clin Orthop 1960; 16: 119-135

S. Hattrup S J. Johnson K A. Chevron osteotomy: analysis offactors in patient dissatisfaction. Foot & Ankle 1985; 5: 27-33

9. Bar-David T, Trepal M J A retrospective analysis of distalchevron and basilar osteotomies of the 1st metatarsal forcorrection of IM angles in the range of 13 to 16 degrees. JFS1991; 30: 450456

IM angle (degrees) Metatarsal Metatarsaldeclination (degrees) length (mm)

Fig. i-Mean postoperativ-e difference. The mean difference inmetatarsal length was 0.428 + 3.08, which was not a significantdifference. The mean metatarsal shortening was 1.81 f 0 873. Thiswas statistically highly significant. The mean change in the IMangle was 8.929 + 2.19. This was also a highly significantdifference. All da ta m ean i SD. I? = 2 and the paired student t-testwas used for data analysis. Key: NS = not significant; * P < 0.5(significant); *- P < 0.01 (very significant); *** P < 0 001 (highlysignificant).

O-l mm (48%)

2 mm (28%) --~. _ 3-4 mm (24%)

Fig. 8-Analysis of postoperative metatarsal shortening. 48% ofpatients (n = 10) had a change of 1 mm or less. 28% (II = 6) had a2 mm shortenmg with 24% (n = 5) having a 3-4 mm sho rtening.

10. Roo t M L. Orien W P, Weed J H. Normal and abnormalfunction of the foot. Clinical Biomechamcs. Volu me 2. LosAngeles. 1977

Il. McMaster M J. The pathogenesis of hallux rigidus. JBJS1978: 60B: 82

12. Carr C R, Boyd B M. Correctional osteotomy for metatarsusprimus varus a nd hallux valgus. JBJS 1968: 50: 135331 367

13. Weissman S D. Radiology of the Foot (2nd Edition).Baltimore. Willlams &Wilkins, 1989; 66-73

14. Sm ith T E The hinge concept in base wedge osteotomies, In:Schlefman B (ed) Doctors Hospital Podiatry InstituteSeminar Manua l. GA: Tucker, 1983; 6666668.

15 Zlotoff H. Shortening of the first metatarsal followingosteotomy and its clmical significance. JAPA 1977, 67.412426.

16. Schuberth J M, Reilly C H, Gudas C J. The closmg wedgeosteotomy: a critical analysis of first metatarsal elevation,JAPA 1984: 74: 13-23.

0 1998 Harcourt Brace & Co. Ltd The Foot (1998) 8, 33-37

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