The influence of open and closed high tibial osteotomy on dynamic patellar tracking: a biomechanical study

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1 Knee Surg Sports Trumtol Arthrosc (7) 15: DOI 1.17/s KNEE The influence of open nd closed high tibil osteotomy on dynmic ptellr trcking: biomechnicl study Robert Gsbeek Æ Roy Welsing Æ Mrco Brink Æ Nico Verdonschot Æ Albert vn Kmpen Received: 7 September 6 / Accepted: 3 Jnury 7 / Published online: 5 My 7 Ó Springer-Verlg 7 Abstrct High tibil osteotomy (HTO) cn cuse ltertions in ptellr height, depending on the surgicl technique, the mount of correction nd the postopertive mngement. Altertions in ptell loction fter HTO my led to postopertive complictions. However, informtion on chnges in dynmic ptellr kinemtics following HTO is very limited. We conducted biomechnicl study, to nlyze the effect of open (OWO) nd closed wedge osteotomy (CWO) on ptellr trcking. Using n inventive experimentl setup, we studied the 3D dynmic ptellr trcking in ten cdver knees before nd fter vlgus HTO. In ech specimen, corrections of 7 nd 15 of vlgus ccording to, both, the OWO nd CWO technique, were performed. Ptellr height significntly incresed with CWO nd decresed with OWO. Both, OWO nd CWO led to significnt chnges in the ptellr trcking prmeters tilt nd rottion. We lso found significnt differences between OWO nd CWO. Vlgus high tibil osteotomy incresed the medil ptellr tilt nd R. Gsbeek (&) Deprtment of Orthopedics nd Trumtology, Mender Medicl Center, P.O. Box 15, 38 BM Amersfoort, The Netherlnds e-mil: rd.gsbeek@mendermc.nl A. vn Kmpen Deprtment of Orthopedics, Rdboud University Nijmegen Medicl Center, Th. Crnenln 7, 655 GH, P.O. Box 911, 65 HB Nijmegen, The Netherlnds R. Welsing M. Brink N. Verdonschot Orthopedic Reserch Lbortory, Rdboud University Nijmegen Medicl Center, Th. Crnenln 7, 655 GH, P.O. Box 911, 65 HB Nijmegen, The Netherlnds reduced the medil ptellr rottion. These effects were more profound fter OWO. No significnt differences were found for the effect on medil lterl ptellr trnsltion. These observtions cn be tken into considertion in the decision whether to perform n OWO or CWO in ptient with medil comprtment osteorthritis of the knee. Keywords High tibil osteotomy Ptellr trcking Osteorthtritis Knee Kinemtics Introduction Young ctive ptients suffering from medil comprtment osteorthritis of the knee with vrus lignment cn be treted with high tibil osteotomy (HTO). Depending on the surgicl technique nd postopertive mngement, ltertions in ptellr height cn be induced [, 3, 6, 11, 1, 16, 1]. Open wedge osteotomy (OWO) proximl to the tibil tuberosity, which is gining populrity in recent yers, hs been reported to cuse ptell bj [6, 1, 1]. Closed wedge osteotomy (CWO) hs been shown to led to both ptell bj nd lt [6, 1]. These ltertions in ptellr height hve been ttributed to the proximlistion (CWO) or distlistion (OWO) of the tibil tuberosity following HTO [1]. Furthermore, scrring, dhesions nd contrcture of the ptell ligment re mentioned to cuse lowering of the ptell in CWO [1]. Besides these chnges in ptellr height, other components of ptellr trcking my be ffected by HTO. This my cuse nterior knee pin, ptell locking, crepitus nd limittion of knee motion. Eventully, the ltered ptellofemorl congruency nd contct stress my led

2 Knee Surg Sports Trumtol Arthrosc (7) 15: to ptellofemorl osteorthritis. Furthermore, there is evidence tht ptellr height my ffect the outcome of totl knee rthroplsty [5, ]. Conversely, pre-existing ptellofemorl symptoms my diminish following HTO [7]. Former studies on the effect of HTO on the ptellofemorl joint focus on the stndrd plin rdiogrphic mesurements of ptellr height t one position of knee flexion [,1]. Furthermore, previous studies in this field restrict the dynmic ptellr trcking to rnge of sttic mesurements of the ptell position in few fixed positions of knee flexion [8, 19]. As fr s the uthors re wre of, no study hs been reported tht describes the true dynmic ptellr trcking following HTO. The present study ws conducted to nlyse the chnges in dynmic ptellr trcking fter both, OWO nd CWO. Mterils nd methods Specimens Ten fresh frozen cdver knees were obtined. Degenertive chnges nd dysplsis were evluted nd excluded bsed on stndrd AP, lterl nd ptell rdiogrphs. The specimens were prepred for use in knee joint motion nd loding pprtus [17]. Therefore, tibi nd femur were trnssectioned t bout cm from the knee joint centre. The ends of the bones were potted in utopolymer, which gurnteed identicl positioning during the different surgeries nd mesurements. All soft tissues were preserved. The qudriceps muscle ws seprted in three prts: rectus femoris, vstus medilis, nd vstus lterlis/intermedius. Three mounting pltes were rigidly fixed to the femur, tibi nd ptell, respectively, which enbled the registrtion of the bony segments visible on the CT scns to the globl coordinte system. Herefter, CT scns of ll knees were obtined. Experimentl set up A specilly designed metl frme with hinges on the medil nd lterl side ws put on the tibi under fluoroscopic view. This frme ws designed such tht the position of the hinges coincided with the plnned rottion point (the pex) of the osteotomy. The frme llowed free moving distl prt of the tibi. In this wy, different vlgus ngles within the sme specimen could be simulted. The tibi positions could be set t predetermined ngle. After this, the specimen ws positioned in the loding pprtus. An electromgnetic motion trcking system (3SPACE Fstrk, Polhemus, Colchester, VT, USA) ws used to mesure the ptello-femorl nd tibio-femorl kinemtics of the knee. Three sensors were fixed rigidly to the mounting pltes on femur, tibi nd ptell. The kinemtics were recorded using continuous dt cquisition. The three seprted prts of the qudriceps muscle were loded with 7 N ech nd n dditionl 5 N xil compressive lod ws pplied to the knee, ccording to n erlier published protocol [17, 18]. For the first reference mesurement, three flexion extension movements were performed mnully. Next, stndrd nterolterl pproch ws used. Two centimetres below nd prllel to the joint line Kirschner wire ws inserted to im the osteotomy. First, the proximl cut ws performed. Using n iming device the distl cut ws mde nd 15 bony wedge ws removed proximl to the tibil tuberosity. The fibul ws cut, ccording to the closed wedge HTO technique of Coventry []. The knee ws put bck into the loding pprtus nd the mesurements were repeted in three different positions of the distl tibi: neutrl (Fig. 1), 7 nd 15 vlgus (lterl closed wedge) position (Fig. 1b). After this, medil pproch ws performed, shifting the pes nserinus nd the superficil medil collterl ligment dorslly. A Kirschner wire ws inserted prllel to the joint line. Using guide instrument second wire ws inserted just proximl of the tuberosity in lterl crnil direction in order to obtin n equl osteotomy level in ll knees. Along this wire the osteotomy ws performed. Herefter, flexion extension cycles were recorded in neutrl, 7 nd 15 vlgus (medil open wedge) position (Fig. 1c). All correction ngles were checked with n electronic inclinometer (Cybex, EDI 3). The surgery ws performed under fluoroscopic view. Dt nlysis After the recordings were mde, the Fstrk motion dt were nlysed nd combined with the CT-scnning dt. The 3D motion dt, which were mesured in the globl coordinte system, were trnsformed to ntomic coordintes. The ntomic coordinte systems were bsed on bony lndmrks, which were retrieved from the CT scn contours [1]. In this wy, 3D dynmic model of ech knee ws constructed with locl ntomic coordinte system. As the ptellr kinemtics re lso lrgely dependent on the tibil movements the tibil kinemtics were lso mesured. The clculted ptellr trcking prmeters were:

3 98 Knee Surg Sports Trumtol Arthrosc (7) 15: b c Fig. 1 Schemtic presenttion of the tibi positioned in the specilly designed frme which enbled testing of different vlgus ngles within the sme specimen. Neutrl, b vlgus closed wedge (7 nd 15 ) nd c vlgus open wedge (7 nd 15 ) ptellr height, tilt, rottion, nd lterl medil trnsltion (For definition of prmeters see Fig. ). To quntify the impct of the HTO for ech of the prmeters, the differences of the ptellr kinemtics fter HTO minus the reference ptellr kinemtics of the neutrl mesurements were clculted. Sttistics The three reference mesurements in neutrl position were compred using Two-wy ANOVA. The differences between the four groups, e.g. 7 nd 15 lterl closed wedge, nd 7 nd 15 medil open wedge, were nlyzed by using Two-wy ANOVA t every subsequent flexion step of 5 up to mximl knee flexion ngle of 1. To ssess whether ech group ws sttisticlly different from the non-operted sitution, we clculted whether the difference of the two mesurements (intct minus operted) ws different from zero by clculting if the vlue zero ws within the outcome of the 95% confidence intervl. Significnce ws set t P <.5. Results In generl, the movement ptterns of the ptell in the non-operted knees were similr to wht cliniclly cn be expected nd is described by vn Kmpen nd Huiskes [18]. Typicl exmples of the effects of HTO on ptellr tilt nd rottion in one of the specimen re shown in Fig. 3 nd b, respectively. The group results re grphiclly displyed in Fig. d. They represent the chnge of ptellr kinemtics cused by the HTO, not the bsolute vlues. Ptellr height As expected, lrger tibil correction ngles induced more ptellr height chnges (Fig. ). The OWO resulted in significnt lowering of the ptell. Lrger corrections in the OWO group cused significnt more ptell lowering, wheres more correction in the CWO group resulted in more increse in ptellr height. The chnge of ptellr height ws not relted to the knee flexion. Hence, during knee flexion the position of the ptell in reltion to the tibi ws rther constnt, which resulted in horizontl curves. The men decrese of ptellr height following 7 OWO ws 1.5 mm (rnge.7;1.7) which significntly incresed to. mm (rnge.7;.6) t 15 OWO. The ptellr height fter 7 CWO incresed on verge with. mm (rnge 1.1;.7). At 15 CWO the men increse ws 3. mm (rnge.1;3.6). Figure 5 shows schemtic presenttion of the ptellr height chnges fter open n closed wedge osteotomy. Fig. Definition of ptellr movements rottion rottion tilt tilt trnsltion trnsltion

4 Knee Surg Sports Trumtol Arthrosc (7) 15: Ptell Tilt (deg) Ptellr Tilt Ptellr Rottion b Ptell Rottion (deg) Ptellr tilt Ref 7 deg CWO 15 deg CWO 7 deg OWO 15 deg OWO Fig. 3 Typicl exmples of the effects of HTO on the ptellr tilt () nd rottion (b) of one specimen. Ref: Reference curve of neutrl mesurement A typicl exmple of the effects of HTO on the ptellr tilt is shown in Fig. 3. On verge, OWO nd CWO cused the ptell to tilt more medilly (Fig. b). A trend ws seen of more medil tilt with OWO thn with CWO. Along the flexion extension movement we found no significnt difference between CWO nd OWO t 7 correction, but during the first hlf of flexion significnt differences were found between CWO nd OWO with 15 correction. OWO cused the ptell to tilt more medilly in extension nd showed decrese in dditionl medil tilt while the knee ws brought in flexion. With incresing flexion the difference in medil tilt between the two HTO groups decresed. All groups showed to be significnt different from zero. The men increse of medil tilt following 7 OWO ws 1.7 (rnge.3;.8), which incresed to.9 (rnge 1.8; 6.) t 15 OWO. The men medil ptellr tilt fter 7 CWO incresed with.7 (rnge.;.9). At 15 CWO the men increse ws.5 (rnge.3;.7). Ptellr rottion A typicl exmple of the effects of HTO on the ptellr rottion is shown in Fig. 3b. Both, OWO nd CWO reduced the norml medil rottion of the ptell long the flexion movement of the knee. In generl, OWO showed significnt more reduction of medil rottion thn CWO (Fig. c). No sttisticl difference between CWO nd OWO with 7 correction ws found round the re in the curves where the two lines cross. At 7 OWO correction, the reduction of the medil rottion declined with incresed flexion of the knee. In full flexion this group showed smll increse of medil rottion of the ptell. Incresing the correction ngle from 7 to 15 resulted in significnt reduction of medil rottion nd in some specimen lterl rottion ws induced. No significnt difference ws found between CWO 7 nd 15. During the first hlf of flexion movement the effect of CWO on the ptellr rottion ws not significntly different from zero, nd this ws lso seen for the 7 of correction with OWO ner full extension. The men reduction of medil rottion following 7 OWO ws 1.6 (rnge.6;.8), which incresed to 5. (rnge.7; 5.5) t 15 OWO. The men medil rottion fter 7 CWO decresed with 1. (rnge.1; 1.9). At 15 CWO the men reduction ws 1.1 (rnge. 1.9). Ptellr medil lterl trnsltion We found poor reproducibility of the differences in medil lterl ptellr trnsltion leding to high stndrd devitions. No significnt differences were found between groups in medil or lterl trnsltion of the ptell (P >.5). Also, ll clculted effects were not different from the reference ptellr-trcking pttern (Fig. d). Discussion Previous observtions of ptellr height fter HTO concern either the closed wedge or the open wedge technique. To our knowledge, only three studies nlyzed the effects on ptellr height in OWO versus CWO. Tigni et l. [16] used Cton s Index (CI) nd showed lowering of the ptell more often with OWO thn with CWO nd high degree of ptell

5 98 Knee Surg Sports Trumtol Arthrosc (7) 15: Ptell height (mm) Ptellr Height High Low b Ptellr Tilt (deg) 7 deg CWO 15 deg CWO 7 deg OWO 15 deg OWO Ptellr Tilt Knee flexion (deg) c Ptellr Rottion (deg) Ptellr Rottion Knee flexion (deg) - Trnsltion (mm) Ptellr medil-lterl Trnsltion 3,5 3,5 1,5 d 1,5 -, ,5 Fig. Averged group ptellr kinemtics: ptellr height (), ptellr tilt (b), ptellr rottion (c) nd ptellr medil-lterl trnsltion (d). The dt represent the chnge of ptellr trcking prmeters cused by the different HTO techniques, not the bsolute vlues. Becuse of clrity stndrd devitions re not shown b Fig. 5 Schemtic presenttion of the chnges in ptellr height fter high tibil osteotomy. Preopertive, b lowering of the ptell fter open wedge osteotomy nd c incresed ptellr height fter closed wedge osteotomy proximlistion in the ltter. Brouwer et l. [] found more ptellr lowering fter n open wedge HTO. They pplied both the Insll Slvti (ISI) nd the Blckburne-Peel Index (BPI). Hoell et l. [9] mesured ptellr height chnge with the ISI nd found no difference between OWO nd CWO. However, this does not exclude true chnge of ptellr height in reltion to the joint line, s the ISI represents the length of the ptellr tendon. Furthermore, BPI nd CI c do not ccurtely mesure the ltertion of ptellr height fter vlgus HTO, becuse they re dependent of the tibil inclintion nd the ntero-posterior trnsltion of the proximl tibi [1]. The present study hs the dvntge of continuous 3D monitoring of the ptell movements, without the limittions of the mesurements of ptellr height on plin roentgen films. We found significnt increse in ptellr height fter CWO nd significnt lowering of the ptell fter OWO. These height chnges were dependent on the mount of correction nd more profound fter OWO s compred to CWO (Fig. ). Concerning the biomechnics of the ptell movement in reltion to its ntomicl position contrdictory informtion in literture is found. Investigtions of the mechnics of ptell bj hve found tht low-riding ptell does not necessrily led to n increse in ptellofemorl contct forces [13, 15]. However, others report n increse in ptellofemorl joint rection force s result of dhesions of the ptell ligment [1]. During surgery we observed tht the proximl trnsltion fter CWO ws limited by the medil nd lterl retinculum to such extend tht the ptellr

6 Knee Surg Sports Trumtol Arthrosc (7) 15: tendon relxed nd curled up. This phenomenon might well be one of the fctors tht led to shortening nd dhesions of the ptellr tendon tht is reported fter CWO [1]. Weidenhielm et l. reported on seven ptients before nd fter CWO using kinemtic nlysis with roentgen stereophotogrmmetric nlysis (RSA). They found no significnt chnge in ptellr rottion nd trnsltion during knee motion, with inconsistent chnges in ptell position [19]. However, they were not informed bout qudriceps tension nor did they correct for relxtion or contrction of the qudriceps muscles during the RSA mesurements. This might hve been lrge confounder in their study. During flexion of the knee, until the ptell is well seted, its stbility rests solely on muscle tension. Hungerford et l. [1] stted tht the congruence of the ptellofemorl joint nd the muscles forces provide considerble stbility irrespective of restrining ligments. Becuse of this we pplied constnt lod to the qudriceps muscle during our experiments (See Mteril nd methods). Hill et l. [8] used mgnetic resonnce imging to mesure ptellofemorl kinemtics through rnge of loded flexion before nd fter CWO in four ptients. They found decrese in ptell flexion nd internl spin ( medil rottion in this study), nd n increse in medil ptellr tilt nd proximl trnsltion. Although this study represents semi-dynmic setting, our results corroborte with their findings. We found tht vlgus osteotomy incresed the medil tilt nd reduced the medil ptellr rottion. These effects were more profound fter OWO. The incresed medil ptellr tilt cn be explined by the incresed lterl pull on the ptell. The tuberosity is locted more lterlly fter vlgus high tibil osteotomy. The lterl ptellr fcet is pressed ginst the lterl wll of the trochle nd the ptell is forced up the lterl groove leding to medil tilt. As the qudriceps tendon remins to hve the sme loding direction, the lterliztion of the tuberosity induces lterl rottion (reduction of medil rottion). Theoreticlly, the effect on the ptellr medil lterl trnsltion is lrger ner full extension of the knee. During flexion the ptell enters the trochler groove, which will enhnce medil lterl stbility. Furthermore, there is reltively high vrition in ptellr position in the lower rnge of flexion. These phenomen my explin why no significnt differences in ptellr trnsltion could be detected. Furthermore, during our experiments we observed tht OWO, led to more tension on the ptell ligment nd the retinculi in contrst to the closed wedge osteotomies, in which we observed reltive relxtion of the ptellr tendon. This my explin why more effect of the HTO ws observed in the OWO group. It seemed tht the distlistion nd incresed tension following OWO, enhnces the forces t the ptellofemorl joint, leding to more obvious effects on the ptellr trcking. If these effects re unwnted, different opertion technique hs been described recently, to prevent the distlistion of the tibil tuberosity with OWO by performing distl tuberosity osteotomy [6]. To our knowledge, the current pper is the first to describe the continuous 3D ptellr trcking chnges following HTO, ccording to both the CWO s the OWO technique. This study clerly shows the evident influence of HTO on ptellr position nd the ptellofemorl movements. The effects of OWO proof to be more profound thn those following CWO, especilly t lrger vlgus corrections of the tibi. These effects of HTO on ptellr height nd ptellr trcking my be of miniml clinicl relevnce but in extensive open wedge corrections the effects my be quite lrge nd led to dverse events with respect to the ptellofemorl joint (e.g. pin, mltrcking or even ptellr (sub)luxtion). On the other hnd, ptellofemorl complints my subside fter high tibil osteotomy. In conclusion, the decision whether closed or n open wedge technique is performed, for the tretment of ptients suffering from medil osteorthritis of the knee, the presence of ptellofemorl complints or pre-existent ptell bj should be tken into considertion. Especilly in lrge open wedge corrections significnt chnges in ptellr height nd trcking cn be induced. In the future, the effect of the kinemtic chnges in the ptellofemorl joint fter high tibil osteotomy in terms of clinicl presenttion nd rdiogrphic chnges fter long term follow-up hve to be determined. References 1. Brink M, Meijerink H, Verdonschot N, vn Kmpen A, de Wl MM (6) Asymmetricl totl knee rthroplsty does not improve ptell trcking: study without ptell resurfcing. Knee Surg Sports Trumtol Arthrosc [Epub hed of print]. Brouwer RW, Bierm-Zeinstr SM, vn Koeveringe AJ, Verhr JA (5) Ptellr height nd the inclintion of the tibil plteu fter high tibil osteotomy. The open versus the closed-wedge technique. 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