Vpliv asimetrije kolčne glavice na tveganje za nastanek zgodnje artroze kolka po Perthesovi bolezni

Moličnik, Andrej (author), Dolinar, Drago (mentor), Kralj Iglič, Veronika (comentor)

IZVLEČEK Izhodišča: Legg-Calvé-Perthesova bolezen (LCPB) kolkov predstavlja povečano tveganje za razvoj artroze kolka kasneje v življenju. Pri osteonekrozi v otroštvu spremenjene mehanske lastnosti kosti lahko privedejo do težav v njihovi rasti in posledično deformacij kolčnega sklepa ter medenice v odrasli dobi. Biomehanska analiza kolkov omogoča dodaten vpogled v mehanizme, ki vodijo do avaskularne osteonekroze v kolku in njenih kasnejših posledic. Metode dela: Na populaciji 141 odraslih kolkov pri bolnikih, ki so preboleli LCPB v otroštvu (testna skupina), smo poleg določitve rezultantne kolčne sklepne sile in kontaktnega kolčnega sklepnega tlaka preučili tudi vpliv različne deformacije artikulacijske površine glavice kolka v frontalni in sagitalni ravnini na njihove vrednosti in vrednosti ostalih biomehanskih parametrov. Kontralateralni zdravi kolki (n = 111) so bili obravnavani kot kontrolna skupina. Biomehanske parametre smo določili s pomočjo dveh matematičnih modelov, ki sestavljata metodo HIPSTRESS: modela za rezultantno kolčno sklepno silo pri stoji na eni nogi in modela za kontaktni kolčni sklepni tlak. Vhodne spremenljivke predstavljajo geometrijski parametri kolčnega sklepa, ki jih določimo iz standardnih anteroposteriornih rentgenskih posnetkov medenice. Z dodatno analizo aksialnih rentgenogramov in nadgradnjo matematičnega modela smo preučili vpliv neenakomerne ukrivljenosti kolčne glavice v frontalni in aksialni ravnini na biomehanske parametre in tveganje za nastanek zgodnje artroze kolka po preboleli LCPB. Analizirali smo vpliv deformacije sklepne površine glavice kolka v frontalni in aksialni ravnini s predpostavko sferičnosti (cirkularnost obrisa sklepne površine glavice), pri dodatni nadgradnji modela pa upoštevali morebitno odstopanje artikulacijske površine glavice od sferičnosti s predpostavko elipsoidnosti (obris sklepne površine glavice cirkularen v frontalni ravnini in elipsoiden v sagitalni ravnini). Opravili smo tudi ločeno analizo teh vplivov na podskupinah kolkov, ki so se po preboleli LCPB razvili normalno glede geometrijskih parametrov ali pa so postali deformirani. Pri tem smo iskali morebitne indikatorje za povečan razvoj artroze kolka po preboleli LCPB. Rezultati: Meritve deformacije sklepne površine v obeh ravninah s predpostavko sferičnosti površine so pokazale, da je vpliv takšne deformacije (različen polmer artikulacijske površine v obeh ravninah) na maksimalni kolčni sklepni tlak manjši od 3 %, kar je manj kot ocenjena napaka meritve (Kocjančič in sod. 2014). Nadaljnja analiza deformacije sklepne površine (tako v testni kot kontrolni skupini) s predpostavko elipsoidnosti deformacije (obris sklepne površine glavice cirkularen v frontalni ravnini in elipsoiden v sagitalni ravnini) je pokazala, da so kolki v anteroposteriorni smeri v povprečju večinoma sploščeni oziroma razpotegnjeni (večja anteroposteriorna polos od frontalne), čeprav so nekateri nasprotno od tega zoženi (manjša anteroposteriorna polos od frontalne). Pričakovano so bili kolki iz testne skupine znatno (za 83 %) in statistično značilno (p < 10–3) bolj deformirani (sploščeni) ter so imeli statistično značilno (p < 10–9) večjo polos (polmer) v frontalni ravnini (za 13 %). Maksimalni kontaktni kolčni sklepni tlak in tudi njegova normalizirana vrednost (glede na telesno težo) ter nosilna sklepna površina se med skupinama niso pomembno razlikovali, so pa bile vse ostale povprečne vrednosti biomehanskih parametrov pomembno in statistično značilno manj ugodne v testni skupini (Wibergov CE-kot, funkcionalni kot obremenitve, položaj pola sklepnega tlaka, indeks gradienta kolčnega sklepnega tlaka in njegova normalizirana vrednost na telesno težo). Primerjali smo skupino kolkov, ki so se razvili s frontalnim polmerom (polosjo), večjim od 2,65 cm, in tiste s frontalnim polmerom (polosjo), manjšim od 2,65 cm. Večino kolkov (80 %), ki so se razvili s frontalnim polmerom (polosjo), večjim od 2,65 cm, so predstavljali kolki iz testne skupine (po preboleli LCPB). Preostali del te skupine (20 %) so predstavljali kontrolni kolki. Kolki s frontalnim polmerom, večjim od 2,65 cm, so bili izrazito (za 125 %) in statistično značilno (p < 10–9) bolj sploščeni v anteroposteriorni smeri ter so imeli statistično značilno manj ugoden (manjši) CE-kot in tudi (manjši) funkcionalni kot obremenilne površine ter (manj negativen) indeks gradienta kolčnega sklepnega tlaka. Primerjava podskupin kolkov, ki so se razvili s polmerom artikulacijske površine v frontalni ravnini pod 2,65 cm (49 % kolkov testne skupine in 84 % kolkov kontrolne skupine), je pokazala podobno neugodne in statistično značilne razlike v prej omenjenih biomehanskih parametrih v podskupini testnih kolkov. Tudi tukaj so bili testni kolki statistično značilno (p = 0,037) bolj deformirani (za 55 %) in tudi tukaj ni bilo značilnih razlik v maksimalnem kontaktnem kolčnem sklepnem tlaku. Primerjali smo tudi skupine displastičnih kolkov z nedisplastičnimi. Razvrstitev displastičnih kolkov (to so kolki, katerih vrednost Gp je večja od 0) glede na metodo HIPSTRESS je razkrila 26 % displastičnih kolkov (n = 66), pri čemer so veliko večino (85 %) te skupine predstavljali testni kolki (po preboleli LCPB). Razvrstitev displastičnih kolkov glede na CE-kot (to so kolki, katerih vrednost CE je manjša od 20°) je razkrila 17 % displastičnih kolkov (n = 43), pri čemer so veliko večino (93 %) te skupine predstavljali testni kolki (po preboleli LCPB). Primerjava teh skupin z ustreznimi skupinami nedisplastičnih kolkov je pokazala bolj ugodne in statistično značilne vrednosti vseh biomehanskih parametrov v nedisplastičnih skupinah. Poleg tega so imeli kolki v obeh displastičnih skupinah statistično značilno večji frontalni polmer sklepne površine in večjo deformacijo. V displastični skupini kolkov glede na CE-kot je bil polmer večji za 19 % (p < 10–13), deformacija pa za 89 % (p < 10–3), v displastični skupini glede na metodo HIPSTRESS pa je bil polmer večji za 17 % (p < 10–13), deformacija pa za 86 % (p < 10–4). Korelacije med parametri, ki v modelu niso funkcionalno povezani, so bile statistično signifikantne. Močna pozitivna korelacija med polmerom artikulacijske površine v frontalni ravnini in deformacijo glavice je v glavnem posledica vpliva testnih kolkov, čeprav posamezni kolki iz kontrolne skupine z večjim polmerom artikulacijske površine v frontalni ravnini dobro sovpadajo v ta korelacijski vzorec. Večina glavic je bila sploščena v anteroposteriorni ravnini ( > 0) in med njimi so bili kolki iz testne skupine v povprečju bolj deformirani. Večina kontrolnih kolkov ima vrednosti indeksa gradienta kolčnega sklepnega tlaka pod pražno vrednostjo za displazijo (Gp = 0) glede na metodo HIPSTRESS, medtem ko so kolki iz testne skupine razporejeni pretežno ob pražni vrednosti za displazijo ali nad njo, in to ne glede na deformacijo (). Zaključek: Ugotovitve naše raziskave potrjujejo prejšnje ugotovitve, da povečanje glavice po preboleli LCPB kompenzira vrednosti maksimalnega kontaktnega kolčnega sklepnega tlaka. Poleg tega podpirajo predlagano vlogo indeksa gradienta kolčnega sklepnega tlaka pri razvoju obkolčja in kažejo na to, da je povečano tveganje za razvoj artroze po preboleli LCPB posledica sočasne displazije s statistično značilno manj ugodno distribucijo tlaka in tudi manjšim CE-kotom.

• Language: Slovenian
• Keywords: biomehanska analiza, kolčni sklepni tlak, Legg-Calve-Perthesova bolezen, deformacija kolčne glavice, displazija kolka
• Work type: Doctoral dissertation
• Organization: MF - Faculty of Medicine
• Year: 2019
• PID: 20.500.12556/RUL-113429
• COBISS.SI-ID: 303463936
• Publication date in RUL: 03.01.2020

Secondary language

• Language: English
• Title: The impact of femoral head asymmetry on the early development of hip arthritis after Legg Calve Perthes syndrome

Abstract

ABSTRACT Background: The Legg-Calvé-Perthesian disease (LCPD) which affects hips in childhood, represents an increased risk of developing hip arthrosis later in life. Modified mechanical bone properties as a consequence of femoral head osteonecrosis in childhood, may lead to growth problems and, consequently, deformities of the hip joint and pelvis in adulthood. Biomechanical hip analysis may provide additional insights into the mechanisms leading to avascular osteonecrosis in the hip and its subsequent consequences. Methods: We have analysed the biomechanical parameters of 141 hips that were subjected to LCPD in childhood, and distinguished between them and 114 contralateral hips without record of disease and taken as controls. Biomechanical parameters were determined by mathematical models for resultant hip force in one-legged stance and for contact hip stress, which use as an input the geometrical parameters assessed from anteroposterior radiographs.. Analysis took into account also the influence of the possible deformation of the articular sphere in frontal and axial plane on those parameters. Because there were no important influence of femoral head deformation with assumption of sphericity of articular sphere in different planes (different frontal and axial radii of articular sphere) found, we upgraded the mathematical model for stress to account for the deviation of the femoral head shape from spherical with assumption of ellipsoid deformation of articular surface (circular surface in frontal plane and ellipsoid in axial plane). We performed additional analysis of radiograms in both planes with estimation of possible influence of elipsoid deformation on biomechanical parameters. Additionaly we also performed analysis after subgrouping hips accordig to the size of femoral head developed after LCPD and looked for possible indicators responsible for higher risk for cox-arthrosis later in life. Results: Measurement of the deformation of the articular surface showed that some hips (in the test and in the control groups) are flattened, and others are extended in the anteroposterior direction, however, on average, they are mostly flattened. As expected, affected hips (test hips) were considerably (by 83%) and statistically significantly more flattened (p<10-3) with larger articular surface radius in the frontal plane, later being favourable as regards hip stress. However, all other biomechanical parameters that exhibited statistically significant differences (centre-edge angle, functional angle of load bearing area, position of the pole, index of hip stress gradient and its normalised value), were less favourable in the test population. No statistically significant differences in peak stress, its normalised value and size of the load bearing area were found between the test and the control groups. We compared 90 hips that developed frontal radius of the articular sphere r larger than 2.65 cm with 165 normal-sized articular surfaces (r smaller than 2.65 cm). Among hips with r>2.65 cm, 72 (80%) pertained to the group of affected hips and 18 (20%) to the control group. Hips with r>2.65 were considerably and statistically significantly more flattened (by 125%), had smaller centre-edge angle and functional angle of the weight bearing area, and had a positive hip stress gradient index but there was no statistically significant difference between both subgroups of hips in peak contact stress and the normalised contact hip stress. We have also focused on the population of 69 affected hips (49% of hips pertaining to the test group) which later developed normal-sized articular surfaces r <2.65 in comparison with 96 contralateral normal-sized articular surfaces r<2.65. The affected hips were considerably (by 55%) and statistically significantly more deformed than the contralateral normal sized hips. Simillary, there was no statistically significant difference between both subgroups of hips in peak contact stress and the normalised contact hip stress but all other biomechanical parameters showed more unfavourable values in hips after LCPD. Analysis of dysplastic and non-dysplastic hips according to the HIPSTRESS method, with hips being dysplastic when hip stress gradient index is positive (Gp>0) and non-dysplastic when hip stress gradient index is negative (Gp<0), showed 26% of all hips being dysplatic (n=66). Grouping hips as dysplastic to the acknowledged criterion of centre-edge angle (<20°) showed 43 dysplastic hips representing 17% of all hips. Dysplastic hips regarding HIPSTRESS and centre-edge angle were mostly from tested group of hips (85% and 93% resopectively). All biomechanical parameters were considerably and statistically significantly more favourable in nondysplastic hips according to both classifications. Dysplastic hips also had considerably and statistically significantly larger radius of the articular sphere in the frontal plane and more deformed articular surface than normal hips. Dyspalstic group according centre-edge angle had for 19% (p<10-13) larger radius and were for 89% (p<10-3) more deformed and dysplastic group according HIPSTRESS criterion had for 17% (p<10-13) larger radius of the articular sphere and were for 86% (p<10-4 more deformed. Correlations between parameters that are not connected functionally within the model showed statistically significant correlations. Strong and positive correlation between the radius of the articular surface in the frontal plane and the deformation of the head were seen, mostly as the contribution of the affected hips although singular unaffected hips which developed large articular surfaces fit well into the correlation pattern. Also, most of the femoral heads are flattened in the anteroposterior direction ( is positive). Amidst the hips that were extended in the anteroposterior direction, the hips affected by the Perthes Disease in childhood are, on average, more deformed. Most of the unaffected hips lie well below the threshold for hip dysplasia (Gp=0) according HIPSTRESS method while, regardless of the deformation parameter , the affected hips are close to the borderline or over the borderline. Conclusion: Results confirm previous indications that head enlargement after the Legg-Calve-Perthes Disease compensates the values of hip stress and supports the suggested role of hip gradient index in the hip developement. Furthermore, it was found that an increased risk for coxarthritis development after the disease is secondary to concomitant hip dysplasia, with considerable and statistically significantly lower centre-edge angle and unfavourable distribution of stress.

• Keywords: biomechanical analysis, hip stress, Legg-Calve-Perthes disease, femoral head deformation, hip dysplasia