POSTGRAD. MED. J. (1964), 40, 531

PATELLECTOMY

RODNEY SWEETNAM, F.R.C.S.Orthopaedic Surgeon, The Middlesex Hospital.

REMOVAL of the patella for fracture beganto be performed towards the end of the lastcentury. Good reports followed the introductionof this novel procedure and everyone seemedsurprised that the results were so good inspite of the removal of what had hitherto beenregarded as a vital link in the quadricepsapparatus. Unfortunately, however, Heineck(1909) in an influential paper strongly con-demned the procedure and there then followeda period when it seems that the operation wasregarded with disfavour. It was not until overtwenty years later, following a paper by Brooke(1937), that patellectomy again became popular.Ever since that time surgeons have withouthesitation considered total removal of this bonean acceptable procedure in certain fractures;some, however, felt that, although justifiedfollowing irrevocable injury, patellectomy it-self so damaged the normal mechanism andpower of the knee that it was only warrantedunder these extenuating circumstances. Theydid not feel that it was justified in patientswith established patello-femoral osteoarthritis,let alone as a method of preventing seriousdissemination of osteoarthritis in knee jointsaffected by early and mild degeneration orchondromalacia of the patello-femoral com-partment alone.

Patellectomy is now an established man-ceuvre, not only in certain fractures, but alsoin patello-femoral osteoarthritis, and even inthe treatment of generalised osteoarthritis whensymptoms and signs, both clinical and radio-logical, suggest that a major part of the painis arising beneath the knee cap.Pathological ConsiderationsFractures

Fractures of the patella are of three types:-Direct violence (comminuted)Muscle violence (transverse)Minor marginal fractures

In considering the operation of patellectomy,we are mainly concerned with severe com-minuted fractures but in some cases also withwidely separated transverse fractures (Fig. 1).

The former are usually the result of a blow ora fall to the ground onto the flexed knee;the latter, a sudden violent contraction of thequadriceps as the patient stumbles.

Often there is wide separation of the frag-ments which, when comminution is present,makes any attempt at reduction quite impos-sible.

Transverse fractures when widely separatedare usually associated with rupture of thelateral expansions at the level of fracture andit is this soft tissue injury, just as much asthe fracture itself, which makes operative re-pair necessary. In this type of fracture it is notalways necessary to remove the patella, foraccurate reduction and firm fixation may beachieved at operation thus ensuring a smootharticular surface when the bone heals.

Patello-Femoral OsteoarthritisChondromalacia patella (Wiles, Andrews

and Devas, 1956) and recurrent subluxation ordislocation are frequent precursors of patello-femoral osteoarthritis. Gradual erosion of thearticular cartilage causes the usual underlyingreactive bone changes until the appearance isidentical with that of osteoarthritis due totrauma, infection, rheumatoid arthritis, or anyof the other known or unknown causes ofpatello-femoral osteoarthritis.

In all cases, progressive wear of the articularsurfaces of the patella and femoral condylesproduce the local symptoms and signs of osteo-arthritis which sooner or later must spread tothe remainder of the knee joint. (Figs. 2 and 3).Indications for PatellectomyFracturesComminuted fractures of the patella usually

produce disruption of the articular surfacewhich, in view of the multiplicity of fracturelines, commonly defy attempts at reduction.Nothing short of "anatomical" replacement canbe accepted, and as this is virtually impossiblein most cases, patellectomy is the most satis-factory treatment.

In transverse fractures, perfect reduction and

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SWEETNAM: Patellectomy

L(a)

FIo. 1.-(a) Widely separated transverse fracture ofthe patella.

firm fixation must be achieved if the bone isto be retained, and if this is not possible, thenthe patella must also be excised.

Osteoarthritis.Early osteoarthritis of the knee beginning in

the patello-femoral part of the joint maycause troublesome symptoms at an early stage.There is very little doubt that removal of thepatella soon after the onset of pain in suchcases, not only rids the patient of the symptoms,but also reduces the likelihood of the degenera-tive arthritis spreading to involve the wholejoint.

In certain patients with late generalised osteo-arthritis of the knee, the predominant symptomsare those due to the osteoarthritic changes inthe patello-femoral joint. When it seems likelythat a significant proportion of the pain isarising beneath the knee-cap, removal of thepatella may well bring about great relief-albeit partial, but none the less welcome.

Pain experienced under the knee-cap ongoing up or down stairs or rising from a sittingposition, particuarly if associated with a feel-ing of crepitus, suggests patello-femoral osteo-arthritis, and when associated with palpablecrepitus and pain on moving the patella on the

(b)FIG. 1.--(b) Comminuted fracture of the patella.

femoral condyles, radiographs are likely toconfirm its presence. In such patients, removalof this source of pain by patellectomy is oftenvery successful indeed.

Recurrent Dislocation of the Patella in AdultsWhereas patellectomy is seldom indicated

in children with recurrent dislocation, in adultswith secondary degenerative changes it is oftenperformed. In most cases some form of realign-ment of the quadriceps apparatus must also bedone to prevent recurrent lateral slipping ofthe central portion of the tendon (West andSoto-Hall, 1958).

Less Common IndicationsRemoval of the patella may be indicated

as part of some other procedure, for examplearthrodesis, arthroplasty or synovectomy, orvery rarely in chronic infection of the boneitself.

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FIG. 2.-Patello-femoral osteoarthritis.

Method of OperationThe choice of operative method must, of

course, depend upon the indication. There are,however, two basic techniques:-

1. Simple enucleation, with the gap beingclosed by suture of the vertical incisionthrough the anterior fibro-tendinoustissue from which the patella has beendissected.

2. Closure of the patellar gap by directtransverse suture of quadriceps tendonto patellar ligament.

In addition, various "plastic" methods ofreinforcing the gap by flaps or advancementswith or without direct suture of quadriceps topatellar ligaments have been advised, but theyare not widely used.

In fracture of the patella a similar choice ispresented in comminuted fractures due to directviolence and therefore unassociated with rup-ture of the lateral expansions. Transversefractures accompanied by complete rupture ofthese expansions, however, are usually repairedby direct suture across the whole breadth of thequadriceps apparatus.

In the absence of damage to the lateral ex-pansions, the choice, therefore, is betweendirect ligament to tendon suture with shorten-ing of the central portion of the quadricepsapparatus, or leaving the gap and relying uponthe strength of the lateral expansions withoutthe possible disadvantage of any disproportion-ate shortening of the patellar portion. In thelatter case, the gap is bridged by the thinpatellar aponeurosis closed vertically by afew catgut sutures.

Closure of the gap transversely by suture ofquadriceps tendon to patellar ligament, notalways an easy procedure, is, I believe, not onlyunnecessary but actually a cause of delayedrecovery of full extension as well as flexion.

FIG. 3.-Patello-femoral osteoarthritis. The changeshere are mainly in the lateral part of the joint.

It is not difficult to understand why recoveryof flexion is delayed, because shortening of thequadriceps complex has occured. The reasonfor the delay in extension is more complicated.

In order to understand why such an ex-tension lag may develop when the centralportion of the quadriceps has been shortened,one has to remember and visualise the lateralexpansions, the importance of which has beenstressed by Hey Groves (1937). Although thin,these broad tendinous bands produce deepmarkings at their sites of insertion into thetibia, thus indicating their strength and powerof muscular pull transmitted to the bonyattachment. Clearly they do not only possessconsiderable strength, but also act with thepatellar portion of the quadriceps in producingextension of the knee, the whole being onefunctioning unit.

Direct suture of quadriceps tendon to patellarligament must shorten the central portion of thequadriceps apparatus by a distance equal tothe height of the patella. This inevitably pro-duces some "bunching up" and therefore re-lative 'lengthening of the lateral expansions,which must disorganise the co-ordinated actionof the quadriceps as a whole, and render anymuscle action exerted through these lateralexpansions much less effective compared witha similar force transmitted through the shorten-ed central portion.

Should it be, therefore, that the patellar part

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of the quadriceps apparatus, probably thestrongest, is the more effective in extendingthe flexed or semi-flexed knee, whereas thevastus medialis and lateralis through the lateralexpansions are largely responsible for securingthe last twenty or so degrees of extension, thenwe should have a ready explanation for thedevelopment of a lag of extension in spite ofclosing the patellar gap transversely. Morethan this-we might reasonably assume thatthe lag was actually caused by the closure withcentral shortening and apparent lengtheningof the lateral expansions. Indeed, no such lagshould, or in my experience does, occur if thegap is not closed in this way.

I believe, therefore, that least damage isdone to the quadriceps at the time of patell-ectomy by simple enucleation of the bonethrough a vertical incision through its anteriorfibro-tendinous covering. The edges of thislayer are later brought together with three orfour quite fine catgut sutures, because, as canbe demonstrated at operation, there is no ten-sion on this line of suture when the knee isflexed; indeed, tension becomes less as flexionincreases.When patellectomy is performed for a trans-

verse fracture it is commonly found that thelateral expansions of the quadriceps are widelytorn on both sides at the level of fracture. Thesubsequent repair of the whole width of thequadriceps at this level usually results in almostequal shortening of central and lateral por-tions. This is because there is a certain amountof overlapping of the thin lateral expansionsas they are repaired; a fortunate occurrence,for in this way relative shortening of the centralportion is avoided and a subsequent lag inextension is unusual.

Operative TechniqueWhen the lateral expansions are intact, the

following simple technique is advised.A small transverse skin incision is best, and

usually it need be only a little longer than thewidth of the patella itself. The anterior surfaceis cleared by dissecting back the upper andlower skin flaps.

Enucleation of the bone is carried out bysharp dissection. A distinct layer of fibro-tendinous tissue runs over and is adherent toits anterior surface, and blends with the quadri-ceps tendon above and patellar ligament below.This layer is incised vertically down to boneand the flaps elevated outwards until theybecome continuous with the lateral expansionson either side (Fig. 4a). The bone is then

w~s~~g~g~ (a)

(b)

FIG. 4.-(a) Elevation of the fibro-tendonous layerduring enucleation of the patella.

(b) Closure of the defect by approximationof the lateral fibro-tendonous flaps.

grasped with a towel clip or similar instrumentand its remaining peripheral ligamentous andsynovial attachments freed.The central defect in the quadriceps, left

by the enucleation of the patella, is simplyclosed by approximation of the two lateralflaps by a series of quite fine plain catgutsutures (Fig. 4b). It can readily be demon-strated that this vertical suture line is not undertension when the knee is flexed; indeed flexiontends to bring the edges together. In time thesethin fibro-tendinous flaps hypertrophy, in somecases even producing bone from remainingremnants of detached periosteum. The centralportion of the quadriceps tendon thus becomesfirmly united to the patellar tendon withoutshortening.Damaged Lateral Expansions. Fractures of

the patella caused by indirect violence arefrequently widely separated and accompaniedby tearing of the lateral expansions. In suchcases, when patellectomy is indicated, great

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September, 1964 SWEETNAM: Patellectomy 535

care must be taken to repair these expansionsafter the fragments of bone have been removed.No special description of the technique is

necessary. The transverse tear of the wholequadriceps apparatus is usually repaired withstout chromic catgut and in this case thequadriceps tendon firmly approximated to thepatellar ligament. No harm comes from thisdirect suture because the lateral expansionswill have been shortened by an equal amountby the natural slight bunching and overlapwhich occurs along the transverse suture line.

After TreatmentThe traditional post-operative management

requires four to six weeks' immobilisation ofthe knee in full extension, followed by severalfurther weeks of protected weight bearing witha plaster backslab. Indeed, in patients in whomthe lateral expansions have been torn andrepaired at operation, this is still the bestroutine to follow. After enucleation of thepatella, however, immobilisation and protectionis quite unnecessary.

After operation no more than a light wooland crepe pressure dressing is required. Nosuture line is under tension, so that no othersupport is necessary. Static quadriceps exer-cises commence on the day after operation,flexion exercises on the fifth day, and walking,at first with reduced weight on the leg usingcrutches, two days later.When the wound is soundly healed and the

patient walking independently with crutchesor sticks, he is encouraged to enter a rehabilita-tion centre where progress is usually more

rapid than in an Out-patient PhysiotherapyDepartment.CommentRemoval of the patella is now a common

operation, and provided that the correct indica-tions are observed, the end result is usuallygood. Many different techniques of operationare employed and their very number suggeststhat the final results probably differ little onefrom another. I have no doubt, however, thatthe simple technique described combined withearly post-operative mobilisation produces avery good result in the great majority ofpatients, not only more quickly than by othermethods, but at the expense of less effort inthe post-operative period.The long-term results of removal of the

patella in man do not suggest that its absencegives rise to excessive wear or degenerativechange in the articular surface of the femoralcondyles (West, 1962). Experimental evidence,however, does indicate that such wear occursafter patellectomy in the rabbit (Bruce andWalmsley, 1942).

Certainly the good long-term results in manconfirm that any harmful effect must be slightand of little consequence when compared withthe known benefits of the operation. From thepurely mechanical view as well, we know thatjoint function is so little impaired that anyreduction in performance is usually so slightas to prove unnoticed. Indeed, Brooke (1937)has expressed the view, which he bases uponexperimental evidence, that the mechanicaladvantage of the quadriceps is actually improv-ed by patellectomy!

REFERENCESBROOKE, R. (1937): The Treatment of Fractured Patella by Excision. A Study of Morphology and Function,Brit. J. Surg., 24, 733.BRUCE, J., and WALMSLEY, R. (1942): Excision of the Patella. Some Experimental and Anatomical Observa-

tions, J. Bone Jt. Surg., 24, 311.EvANs, D. K. (1962): Osteomyelitis of the Patella, Ibid., 44 (B), 319.GROVES, Hey E. W. (1937): A Note on the Extension Apparatus of the Knee Joint, Brit. J. Surg., 24, 747.HEINECK (1909): The Modern Operative Treatment of Fractures of the Patella, Surg. Gynec. Obstet., 9, 177.WEST, E. E., and SOTO-HALL, R. (1958): Recurrent Dislocation of the Patella in the Adult, J. Bone Jt. Surg.,40 (A), 386.WEST, E. E. (1962): End Results of Patellectomy, Ibid., 44 (A), 1089.WILES, P., ANDREWS, P. S., and DEVAS, M. B. (1956): Chondromalacia of the Patella, Ibid., 38 (B), 95.

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