The Journal of Arthroplasty xxx (2014) xxx–xxx

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The Journal of Arthroplasty

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Medial Over-Resection of the Tibia in Total Knee Arthroplasty for VarusDeformity Using Computer Navigation

Kenneth A. Krackow, MD b, Sivashanmugam Raju, MS Ortho b, Mohan K. Puttaswamy, MBBS, MS Ortho a

a Department of Orthopedic Surgery, Fortis Hospital, Bangalore, Indiab Department of Orthopedic Surgery, Buffalo General Hospital, Buffalo, NY

a b s t r a c ta r t i c l e i n f o

The Conflict of Interest statement associated with thidx.doi.org/10.1016/j.arth.2014.11.034.

Reprint requests: Dr. Mohan K. Puttaswamy, FortisBangalore, India-560 076.

http://dx.doi.org/10.1016/j.arth.2014.11.0340883-5403/© 2014 Elsevier Inc. All rights reserved.

Please cite this article as: Krackow KA, et al,Navigation, J Arthroplasty (2014), http://dx.

Article history:Received 24 June 2013Accepted 25 November 2014Available online xxxx

Keywords:medial overresectionvarus OA kneenavigated TKAreduction osteotomytension stress examination

We are reporting a series of 35 cases in which downsizing, lateralizing of the tibial baseplate and resection of theuncovered medial plateau bone releases the medial collateral ligament and tightens the lateral collateral liga-ment. Result in excellent ligamentous balance and correction to neutral mechanical axis. The mean follow upwas 32.8 months (11-95 months) and the average pre-operative varus was 9.47° (3.5-15°) with the averagepost-operative alignment was 0.65° varus. We obtained a mean correction of 0.45° for every mm (millimeter)of bone resected. We did not have any varus collapse or instability. Medial Over-resection could be employedas a technique in the management of varus OA knee with 2 mm of resection giving about 10 correctionof deformity

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Varus deformity that is not passively correctable at the time of totalknee arthroplasty requires sequential soft tissue releases on the concave(medial) side [1]. A technique of resection of the medial edge of the cutsurface of the tibia to decompress themedial soft tissue sleevewas prac-ticed independently by the senior author (KAK) for the past 10 years.Dixon et al. described a case series using this technique and reportedthat it was possible to correct varus deformity of 20°- 40°without releas-ingmedial soft tissues other than the deepmedial collateral ligament [2].The tibial tray was downsized and lateralized and the uncapped medialtibial bone was resected, which corrected the varus deformity.

The object of the present paper is to present our experiencewith thistechnique of posteromedial over-resection of the tibial plateau usingcomputer navigation for correction of varus deformity and quantifythe amount of correction obtained with the size of resection of non-osteophytic bone.

Materials and Methods

This is a retrospective reviewof 35 cases of navigated cemented TotalKnee Arthroplasty (TKA) using only the technique of posteromedial tib-ial bone resection for varus deformity correction operated between2004 and 2009. The Stryker TKA triathlon system used permitsdownsizing of the tibial component by one size and thus helps us to lat-eralize the tibial tray. The only soft tissue release done was the deepMedial Collateral Ligament (MCL).

The Clinical data analyzed consisted of patient demographics, KneeSociety Functional score (KFS), Clinical Scoring (KSS) and Lower Ex-tremity Activity Scale (LEAS). 32 patients had complete data and wereused for calculating the correction of deformity, while 26 patients whohad complete scores for KFS, KSS and LEAS was used to assess the func-tional status. The radiological analysis consisted of preoperative andpost-operative assessment of Long Standing Lower Extremity (LSLE)for estimating amount of varus deformity. Individual knee joint X rayswere used to analyze evidence of component subsidence & loosening.Intraoperative data analyzed includes the Navigation data recording ofMaximum varus, Tension Stress and amount of bone resected.The rela-tionships between medial bone resection (mm) and degree of correc-tion was investigated using Pearson product-moment correlationcoefficient. Linear regression analysis was done do find out the relation-ship between variables like maximum varus and amount of bone resec-tion.Preliminary analyses were performed to ensure no violation of theassumptions of normality, linearity, and homoscedasticity.

Surgical Technique

The standard skin incision used by the senior author is a lateralMull-er incision extending from the midline above the patella to the lateralborder of the middle of the patella, to a point just lateral to the anteriortibial crest. The joint is exposed through a standard medial parapatellarcapsular exposure with release of deep MCL as part of the exposure.Threaded pins for the trackers of the navigation system (Stryker,Mahwah, NJ) are inserted into the femur just proximal to the articularsurface and into the tibia potentially out of theway of the tibial externalalignment jig. Registration of the hip center is done.The distal end of thefemur, the articular surface of the tibia and the center of the ankle joint

e Arthroplasty for Varus Deformity Using Computer

Table 1Patient Raw Data for Medial-Overresection and Outcomes.

Pre-OpVarus

DeformityTensionStress

MedialResection Correction

Correction permm of

ResectionFinal

Alignment

A 15.5 15.5 11 15 1.4 0.5B 9.5 9.5 10 9.5 1.0 0C 8 7 6D 8.5 8.5 11 8.5 0.8 0E 11 10 11 10 0.9 0F 8 8.5 7 8 1.1 0.5G 4.5 4.5 10 4.5 0.5 0H 5 3.5 5 3.5 0.7 0I 5.5 4.5 6 3.5 0.6 1J 8.5 8 8 7.5 0.9 0.5K 12 11.5 19 11.5 0.6 0L 15 15 1.5M 8.5 8.5 13.5 8 0.6 0.5N 15.5 13.5 13 11 0.8 2.5O 11.5 12.5 10 10.5 1.1 2P 11.5 9 7 8 1.1 1Q 14 11.5 17R 9 6.5 8 4.5 0.6 2S 6.5 5.5 6 5 0.8 0.5T 9.5 6.5 8 6 0.8 0.5U 9 8.5 10 8 0.8 0.5V 14 12 3 11.5 3.8 0.5W 4.5 4 3 4 1.3 0X 13 12 10 10 1.0 2Y 8 7.5 6 7.5 1.3 0Z 3.5 3 6 2.5 0.4 0.5AA 11 8 6 5.5 0.9 1.5AB 6 5 2 5 2.5 0AC 16 14 20 14 0.7 0AD 7.5 6 10 5.5 0.6 0.5AE 11.5 9.5 7 9 1.3 0.5AF 11.5 7.5 5 6.5 1.3 1AG 14.5 12 12 10.5 0.9 1.5AH 8 6 3 6 2.0 0AI 6.5 3 7.5 2.5 0

2 K.A. Krackow et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx

are registered as per the navigation protocol. The resting position of theknee, maximum varus, maximum valgus and deformity on the Tension-Stress examand knee range ofmotion are recorded [1]. In Tension stressexamination tibia is held distracted from the femur and the capsular-ligamentous complex is taut in both medial and lateral aspects. Thisgives the true deformity to be addressed to achieve proper balance.Correction achieved by medial resection alone was calculated bysubtracting tibio-femoral alignment in tension stress from the preoper-ative varus deformity. Tension stressmeasures the amount of correctioncontributed by the soft tissues and eliminates the risk of any over esti-mation of the correction by medial bony resection.

Medial and posteromedial osteophytes are removed. No medial softtissue release is done except for the deep medial collateral ligament. Lig-ament balance is assessed using the tension-stress exam. Trial femoraland tibial components are inserted and deformity and stability areassessed in extension and flexion, using navigation. If there is persistentvarus, the trial components are removed and a tibial tray that is one sizesmaller is placed at the lateral edge of the cut surface of the tibia. Thepros-thesis used (Triathlon, Stryker, Mahwah, NJ) allows tibial componentsone size smaller for every size of the femoral component. We usedmetal backed tibial component in all cases. The uncovered tibial condylarbone medial to the tibial tray is resected using a saw oriented in a planeparallel to the mid-sagittal plane from a proximal-to-distal direction(90°to the tibial plateau), with the knee held in maximum flexion. The bonefragment is freed from its soft tissue attachments and is removed. Align-ment is assessed again using navigation till zero mechanical alignmentis obtained. Further medial soft tissue release, which has not been neces-sary in our series, may be done at this time. Once satisfactory alignment isachieved, the trial components are removed and final implants arecemented in routine fashion. The femoral component is cemented in rel-ativelymedial position on the femur. Final alignment and range ofmotionare recorded. The wound is closed in routine fashion over a suction drain.Standard pain and rehabilitation protocols were followed in all patients.

Results

35 patients were part of the study. Follow-up was for an average of32.8 months (range: 11-95months). The average pre-operative deformi-ty was 9.47° varus (range: 3.5°-15.5° varus). The average post-operativealignment was 0.65° varus (range 0°- 2.5° varus). No patient in thestudy was lost to follow-up. Complete KSS and KFS data was present in26/35 of patients and has been used in the final analysis. The KSS im-proved from 38(10-83) to 89.2 (57-100) while the KFS improved from51.45(30-90) to 76.55 (45-100). There was improvement in the activityscores on LEAS from a mean of 8 (6-11) to 9.68(6-12). Two patients ex-pired during follow-up due to unrelated causes. There were no revisionsduring the follow-up period. There was one patient with acute infectionwho was treated with debridement and liner exchange. Table 1 showsthe data of our patients with correction achieved. The salient statisticaloutcomes in the patients arementioned in Table 2. Therewasno evidenceof component loosening, functional instability in any of our patients.

The navigation data indicate that all the correction was achievedthrough the resection of uncapped medial tibial bone.At last follow-up,none of the knees had x-ray evidence of component migration. Therewas a strong positive correlation between the two variables, r = 0.62,n = 32, p b .0001, with 38.1% shared variance.The equation listed onthe scatter plot below shows that every 1 mm of medial bone resectionthere is a Varus deformity correction of 0.45° as shown in Fig. 1.

We were unable find out if any one soft tissue variable that deter-mines the amount of bone needed to be resected because all the soft tis-sue variables were inter-related and shows multi-collinearity.

Discussion

Varus gonarthrosis can be corrected at total knee replacement sur-gery by a combination of various methods, including soft tissue release

Please cite this article as: Krackow KA, et al, Medial Over-Resection of theNavigation, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.11

that can be done as a periosteal sleeve off the tibia [1,3] discrete releaseof the medial superficial collateral ligament and pes anserine tendons[4], pie-crusting of the superficialmedial collateral ligament [5]and fem-oral medial epicondylar osteotomy [6]. Each technique has its own ad-vantages and disadvantages. Extensive sub-periosteal stripping of theproximal medial tibial soft tissue sleeve can result in more bleedingand discrete release of medial ligaments and tendons can destabilizethe knee [4,7,8]. Dixon et al [2] described a technique of resecting theuncappedmedial tibial bone after downsizing and lateralizing the tibialtray, that was used to correct severe varus deformities. The senior au-thor(KAK) of this paper has practiced this technique independentlyfor over 10 years. In this paper, we examine the effect of this techniqueon varus deformities as evaluated by computer-assisted navigation.

The concept involved in this technique is that the intact medial softtissue sleeve is decompressed by resecting the medial tibial bone. Softtissue stripping is limited to the deep medial collateral ligament andthat attached to the resected bone fragment. The advantage is lessbleeding and little or no risk of instability. The tibial tray is downsizedby one, which is possible for every femoral component size in the sys-tem we used (Triathlon, Stryker, Mahwah, NJ), and the smaller tray ispushed to the lateral edge of the cut tibial surface. Themedial soft tissuesleeve undergoes a relative lengthening after the resection of the bonethus uncovered. This lengthening was enough to completely correctthe varus deformities that we have presented in this paper. Deformitiesthat are of a higher varus anglemight possibly need a concomitant stan-dard graduated medial sleeve release.

It was noticed during surgery that the effect of lateralizing the tibialtraywas two-fold as shown in the illustration (Fig. 2). It causes amedialtranslation of the entire tibia (Fig. 2. 2-3) in order to center the tibial trayunder the femoral component, which is now made possible by the

Tibia in Total Knee Arthroplasty for Varus Deformity Using Computer.034

Table 2Statistical Analysis With Important Outcomes in our Series.

Parameters N Range Minimum Maximum Mean Std. Deviation

Correction (°) 32 12.5 2.5 15 7.734 3.0743Correction per mm of Resection (°/mm) 32 3.4 0.4 3.8 1.113 0.7029Difference Between Tension Stress &Pre-op Varus Deformity (°)

33 5 -1 4 1.227 1.1531

Final Alignment (°) 33 2.5 0 2.5 0.652 0.7233Maximum Valgus (°) 35 14.5 0.5 15 6.886 3.6884Maximum Varus (°) 35 13.5 5.5 19 12.357 3.7858Medial Bone Resected (mm) 35 18 2 20 8.786 4.4611Pre-op Varus Deformity (°) 35 12.5 3.5 16 9.757 3.4966Tension Stress (°) 33 12.5 3 15.5 8.47 3.2281

3K.A. Krackow et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx

decompressive effect of the medial resection.We found that cementingthe femoral component relatively medially on the femur helps in thismedial translation of the proximal tibia. It also, thus takes up any redun-dancy that may be present in the lateral ligament complex, as may bethe case in Krackow Types II, III and IV deformities. This has the effectof increasing the overall stability of the knee, as opposed to the poten-tially destabilizing effects of medial ligament release. In the casewhere the lateral sleeve is redundant to such an extent that translationdoes not improve stability, a posterior-stabilized knee could be used fora certain lateral translational constraint that is inherent in that design

When the medial uncapped bone is resected, the extension spaceoften looks like a trapezoid on tension stress examination, giving theimpression of persistent deformity. We have found that this correctswhen the trial components are inserted and then the knee becomesper-fectly balanced both and in extension. This correction could be an effectof the medial translation of the entire tibia with the tibial tray to centeritself under the femoral component, thus evenly stretching out both col-lateral sleeves.It could also be an effect of balancing- or filling-out theentire soft tissue envelope in three dimensions.

One concern of lateralizing the tibial tray is that the medial edge ofthe tray will now rest on the central core of the tibial plateau, whichconsists of softer bone, potentiating the risk of subsidence. We havenot found that to be the case, as we have consistently observed thatthe bone under the medial tibial articular surface, even after the stan-dard tibial cut, has become hard and eburnated from abnormal weightbearing due to the varus malalignment and the arthritic process. Thissclerotic bone extends toward the midline, more often than not. Thus,the risk of subsidence is minimized and indeed, we have not seen sub-sidence in any of our cases. Mullaji et al found 3 subsidences in their se-ries of 173 knees in 117 patients after using an all poly tibia out of whichjust one patient needed revision [9]. This difference could possibly bebecause of bony quality in different races. In a recent publication byMullaji et al looking into the amount of correction in 71 patients usingnavigation, approximately 2 mm of bone resection was needed toachieve 1 degree of correction [10]. The difference in our technique

y = 0.4468x + 3.9711R² = 0.3806

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25

Var

us D

efor

mity

Cor

rect

ion

(°)

Medial Bone Resection (mm)

Relationship of Amount of Medial Bone Resection (mm) Resulting in Correction of Varus Deformity (°)

Fig. 1. Scatter Plot showing the correlation of the amount of bone resection and the correc-tion obtained.

Please cite this article as: Krackow KA, et al, Medial Over-Resection of theNavigation, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.11

with their study was we lateralized the tibial component and resectedthe uncapped bone till a perfect correction was obtained but Mullajiet al hypothesized that 1 degree correction was obtained with 2 mmof resection and resected bone based on their hypothesis. If correctionwas not obtained then in 12/71 patient’s additional soft tissue releasewas done in their study, we did not undertake any soft tissue release;the need for soft tissue release was probably due to the larger deformityin their patient population. Our result confirms their conclusion ofobtaining 1 degree correction for every 2 mm of bone resection.

It was found that a 1-mm width of medial tibial bone resection re-sulted in the correction of nearly 0.45 degree of varus. There is somevariation in the amount of correction obtained in different patients, aswas shown during navigation, with a range of 0.41° to 2° per millimeterof width resected from the tibia. We think that this variation could be afunction of the size of the soft tissue envelope of the knee, the relativesizes of the femur and the tibia and the ‘give’ of the medial and lateralsoft tissue sleeves. We tried to determine which variable(like varusstress..) was associated most with correction but our linear regressionmodel testing showed that we need atleast 90 patients to support thismodel. In the given data set it was found that all the variables wereclosely related andwewere not able to determine an independent rela-tionship with the amount of bone resection but all the variables werestrongly correlated with amount of bone resected. This indicates thatthe translation of tibia is based on the state of the collateral ligamentson either side.

It is the practice of the senior author to use the smallest possiblefemoral component for a given knee without creating a substantial an-terior notching [11]. In combination with that, the benefit of a smallertibial tray would be a smaller prosthetic volume implanted, which im-proves comfort and range of motion by avoiding an overstuffing of thejoint. Some surgeons claim that the femoral component should ‘fit thecut distal surface of the femur’ to have good fixation. This is not neces-sary, as even if the medial-lateral dimension of the femoral componentis smaller than the cut surface of the femur, it does not loosen and theexposed bone at either edge does not cause problems.

This technique can be used as a primary method of correcting allvarus deformities as it has the potential to correct significant amountsof deformity without disturbing the soft tissue sleeve. This in turncould reduce the risk of instability, bleeding and pain and thereby im-prove range ofmotion and function. In principle we think that this tech-nique can also be used to correct sagittal plane deformities (FixedFlexion or Recurvatum) by moving the base plate either anteriorly orposteriorly and removing the corresponding uncovered bone.

Conclusion

Correction of varus deformity in a total knee arthroplasty can bedone by downsizing the tibial tray, lateralizing it and resecting theuncapped medial tibial bone. Our study demonstrates that approxi-mately on average 1 degree correction can be obtained on resection of2 mm of non-osteophytic bone. This technique helps in minimizingsoft tissue releases but also obtain a stable correction of varus deformity.

Tibia in Total Knee Arthroplasty for Varus Deformity Using Computer.034

Fig. 2.Medial Reduction Osteotomy & lateralization of tibial base plate with soft tissue balance.

4 K.A. Krackow et al. / The Journal of Arthroplasty xxx (2014) xxx–xxx

References

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2. DixonMC, Parsch D, Brown RR, et al. The correction of severe varus deformity in totalknee arthroplasty by tibial component downsizing and resection of uncapped proxi-mal medial bone. J Arthroplasty 2004;19(1):19.

3. Teeny SM, Krackow KA, Hungerford DS, et al. Primary total knee arthroplasty in pa-tients with severe varus deformity. Clin Orthop 1991;273:19.

4. EnghGA. The difficult knee: severe varus and valgus. Clin Orthop Relat Res 2003;416:58.5. Verdonk PC, Pernin J, Pinorali A, et al. Soft tissue balancing in varus total knee

arthroplasty: an algorithmic approach. Knee Surg Sports Traumatol Arthrosc 2009;17(6):660.

Please cite this article as: Krackow KA, et al, Medial Over-Resection of theNavigation, J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.11

6. Engh GA, Ammeen D. Results of total knee arthroplasty with medial epicondylarosteotomy to correct varus deformity. Clin Orthop Relat Res 1999;367:141.

7. Whiteside LA, Saeki K, Mihalko WM. Functional medical ligament balancing in totalknee arthroplasty. Clin Orthop Relat Res 2000;380:45.

8. Saeki K, Mihalko WM, Patel V, et al. Stability after medial collateral ligament releasein total knee arthroplasty. Clin Orthop Relat Res 2001;392:184.

9. Mullaji Arun B. Vinod Padmanabhan and Gaurav Jindal. Total Knee arthroplasty forProfound Varus Deformity. J Arthroplasty 2005;20(5):550.

10. Mullaji AB, Shetty GM. Correction of varus deformity during TKA with ReductionOsteotomy. Clin Orthop Relat Res 2014;472:126.

11. Ritter MA, Thong AE, Keating EM, et al. The effect of femoral notching during totalknee arthroplasty on the prevalence of postoperative femoral fractures and on clinicaloutcome. Bone Joint Surg Am 2005;87(11):2411.

Tibia in Total Knee Arthroplasty for Varus Deformity Using Computer.034