Activity level and severity of dysplasia predict age at bernese periacetabular osteotomy for symptomatic hip dysplasia

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1 Washington University School of Meicine Digital Open Access Publications 2016 Activity level an severity of ysplasia preict age at bernese periacetabular osteotomy for symptomatic hip ysplasia Travis Matheney Boston Chilren's Hospital Ira Zaltz Oaklan Orthopaeic Surgery Young-Jo Kim Boston Chilren's Hospital Perry Schoenecker St. Louis Chilren's Hospital Michael Millis Boston Chilren's Hospital See next page for aitional authors Follow this an aitional works at: Recommene Citation Matheney, Travis; Zaltz, Ira; Kim, Young-Jo; Schoenecker, Perry; Millis, Michael; Poeszwa, Davi; Zurakowski, Davi; Beaule, Paul; an Clohisy, John,,"Activity level an severity of ysplasia preict age at bernese periacetabular osteotomy for symptomatic hip ysplasia." The Journal of Bone an Joint Surgery.98, (2016). This Open Access Publication is brought to you for free an open access by Digital It has been accepte for inclusion in Open Access Publications by an authorize aministrator of Digital For more information, please contact

2 Authors Travis Matheney, Ira Zaltz, Young-Jo Kim, Perry Schoenecker, Michael Millis, Davi Poeszwa, Davi Zurakowski, Paul Beaule, an John Clohisy This open access publication is available at Digital

3 665 COPYRIGHT Ó 2016 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED A commentary by Carsten Frank Perka, MD is linke to the online version of this article at jbjs.org. Activity Level an Severity of Dysplasia Preict Age at Bernese Periacetabular Osteotomy for Symptomatic Hip Dysplasia Travis Matheney, MD, Ira Zaltz, MD, Young-Jo Kim, MD, PhD, Perry Schoenecker, MD, Michael Millis, MD, Davi Poeszwa, MD, Davi Zurakowski, PhD, Paul Beaulé, MD, an John Clohisy, MD, on behalf of the ANCHOR Stuy Group Backgroun: The age when patients present for treatment of symptomatic evelopmental ysplasia of the hip with periacetabular osteotomy (PAO) varies wiely. Moifiable factors influencing age at surgery inclue preexisting activity level an boy mass inex (BMI). The severity of the hip ysplasia has also been implicate as a factor influencing the age at arthritis onset. The purpose of this stuy was to etermine whether activity level, BMI, an severity of ysplasia are inepenent preictors of age of presentation for PAO. Methos: A retrospective, institutional review boar-approve review of prospectively collecte ata from a multicenter stuy group ientifie 708 PAOs performe for evelopmental ysplasia of the hip. Demographic factors that were consiere in the analysis inclue age at surgery, BMI, history of hip isorer or treatment, an uration of symptoms. The severity of the evelopmental ysplasia of the hip was assesse by raiographic measurement of the lateral an anterior center-ege angles an acetabular inclination. Activity level was assesse with the University of California, Los Angeles (UCLA) activity score. Spearman correlations an t tests were use for univariable analysis. Multivariable regression analysis using generalize estimating equations was applie to etermine inepenent preictors of age at PAO. Results: Univariable analysis inicate that age at presentation for treatment of PAO correlate with the lateral an anterior center-ege angles (p < 0.001), UCLA score (p < 0.001), an BMI (p = 0.04). Since the lateral an anterior centerege angles were similarly correlate (Spearman rho = 0.61, p < 0.001), the lateral center-ege angle alone was use to classify the severity of the evelopmental ysplasia of the hip. Multivariable linear regression confirme that a high UCLA score an severe hip ysplasia were inepenent preictors of age at PAO (p < 0.001). Conclusions: A high activity level an severe ysplasia lea to the evelopment of symptoms an presentation for PAO at significantly younger ages. The combination of these two factors has an even greater effect on ecreasing the age at presentation for hip-preserving surgery. An increase BMI was not inepenently associate with a younger age at surgery. Moifying activity level may be beneficial in terms of elaying the onset of symptoms from evelopmental ysplasia of the hip. Level of Evience: Prognostic Level IV. See Instructions for Authors for a complete escription of levels of evience. Peer Review: This article was reviewe by the Eitor-in-Chief an one Deputy Eitor, an it unerwent bline review by two or more outsie experts. The Deputy Eitor reviewe each revision of the article, an it unerwent a final review by the Eitor-in-Chief prior to publication. Final corrections an clarifications occurre uring one or more exchanges between the author(s) an copyeitors. Developmental ysplasia of the hip remains the most common cause of hip osteoarthritis 1-4. The incience of ault hip ysplasia is not known as not all affecte hips are believe to evelop symptomatic osteoarthritis. Reports on hips that became symptomatic have escribe risk factors for en-stage arthritis leaing to arthroplasty, incluing increase activity level, high boy mass inex (BMI), female sex, an increase severity of hip ysplasia, with the first two Disclosure: This stuy was fune by Curing Hip Disease, Smith & Nephew Enoscopy, Pivot Meical, an the ANCHOR Fun. On the Disclosure of Potential Conflicts of Interest forms, which are provie with the online version of the article, one or more of the authors checke yes to inicate that the author (or the author s institution) ha a relevant financial relationship in the biomeical arena outsie the submitte work. J Bone Joint Surg Am. 2016;98:

4 666 being consiere moifiable We consier these factors when counseling this typically oler patient group about changing potentially isease-moifying risk factors by losing weight an ecreasing activity. With increasing early recognition of hip ysplasia an wellescribe goo-to-excellent outcomes of joint-preserving surgery, youngerpatients(typicallylessthanfortyyearsofage)aremore commonly being referre for evaluation an treatment before en-stage osteoarthritis has occurre. Prior investigators have reporte the raiographic appearance of hips treate with periacetabular osteotomy (PAO) an have emonstrate that increase severity of ysplasia is associate with a higher risk of en-stage hip osteoarthritis Debate continues as to whether moifiable factors, such as a higher BMI an activity level, increase the risk of hip osteoarthritis an the nee for subsequent total hip arthroplasty. To our knowlege, no one has assesse how these same risk factors affect the age at onset of hip pain an/or the age at presentation for hip-preservation surgery in the aolescent an younger ault (less than forty-year-ol) population. This becomes an important issue when this typically younger patient presents with an inciental fining of hip ysplasia but minimal or no symptoms an inquires about moifications to lifestyle or boy habitus that might affect the onset of symptomatic osteoarthritis. The primary aim of this stuy was to etermine whether moifiable factors such as higher activity level an BMI lea to a ecrease age at presentation for PAO. A seconary aim was to assess whether the severity of ysplasia has an effect on age at PAO an whether there is any aitional effect when it exists in combination with the moifiable risk factors mentione above. Finally, as aolescent an young ault patients with pre-arthritic hip ysplasia often inquire about the typical age at symptom onset, we sought to etermine whether there was a consistent relationship between age at surgery an patient-reporte uration of symptoms. Materials an Methos We conucte a retrospective, institutional review boar-approve analysis of ata that ha been prospectively collecte at nine centers that perform the Bernese PAO. The primary inclusion criterion was symptomatic evelopmental ysplasia of the hip treate with Bernese PAO. Exclusion criteria were any evience of concomitant femoroacetabular impingement morphology, neuromuscular conitions, a history of substantial hip trauma, or connective-tissue isease. When a patient ha bilateral hip ysplasia an ha unergone bilateral PAO, the ate of the first surgery was use to etermine the age at presentation for surgical treatment. On enrollment in this stuy, patients were aske to complete a questionnaire that inclue questions about their preoperative activity level an uration of hip-relate symptoms. We ientifie 756 PAOs performe for symptomatic evelopmental ysplasia of the hip, an complete raiographic an questionnaire ata were available for final multivariable analysis for 708 of these hips. Of the remaining hips, thirty-two ha missing raiographic ata; twenty-six, missing activity scores; an six, missing BMI ata. Demographic an clinical information inclue age at surgery, sex, BMI, uration of hip pain, an activity level. The BMI was categorize as either >30 kg/m 2 or 30 kg/m 2. A history of a hip isorer or treatment may affect the timing of presentation for PAO for hip ysplasia. Therefore, we recore whether patients ha unergone treatment for any other conition relate to hip ysplasia or femoroacetabular impingement. Inclue in this group were patients treate with bracing or surgery for infant or chilhoo hip ysplasia, arthroscopy for a labral tear or impingement, or osteotomy for proximal femoral eformity. Raiographic Measures The severity of the acetabular ysplasia was assesse with stanarize raiographs of the pelvis an hip, incluing anteroposterior an false-profile views. Raiographic measures inclue the lateral center-ege angle of Wiberg, anterior center-ege angle of Lequesne an e Sèze, an acetabular inclination (Tönnis sourcil angle) Raiographs were measure by the treating physician, as a prior stuy ha shown aequate interobserver reliability of such measurements 27 an because of restrictions applie by the institutional review boars of iniviual centers. Patient ata were anonymize before they were submitte to a central ata-collection site. On the basis of prior work 28, centerege angles of >15 to 25 were consiere to inicate mil ysplasia; 5 to 15, moerate; an <5, severe. Acetabular inclination of 10 to 20 was consiere to inicate mil ysplasia; 21 to 30, moerate; an >30, severe. The association between the raiographic appearance of the osteoarthritis an arthritis-relate pain can be variable Aitionally, a primary goal of hip-preserving surgery is to prevent the onset of arthrosis. Thus, no hip that ha greater than Tönnis grae-2 changes (grae 2 = joint space narrowing with subchonral cysts) were inclue in the stuy, an we i not inclue raiographic evience of osteoarthritis as a measure to preict age at surgery 34. Activity Assessment Activity level was assesse with the University of California, Los Angeles (UCLA) activity score (1 to 10), a valiate, reliable, self-reporte metric of physical activity of patients with osteoarthritis of the hip (Fig. 1) 35. To evaluate the relationship between activity level an age at surgery, we subcategorize patients as being minimally active (a UCLA score of 1 to 4), moerately active (5, 6, or 7), or highly active (8, 9, or 10). Duration of Symptoms an Age at Symptom Onset Several factors may contribute to the time that it takes to evelop symptoms severe enough for an iniviual to seek meical avice regaring care. Because of the ifficulty in evaluating an summarizing all possible reasons for a elay in treatment of symptomatic hip ysplasia, the patients were aske the uration of their symptoms before they unerwent surgery. Symptom uration was classifie as less than six months, six to twelve months, one to three years, three to five years, or more than five years. We then assesse whether the uration of symptoms was Fig. 1 The UCLA activity score, which is use to rate activity over the previous six months on a scale of 1 to 10, with 10 being the highest level of activity.

5 667 TABLE I Demographic an Raiographic Variables Assesse for Effect on Age at PAO No. of Hips* Mean Age at PAO an Stan. Dev. (yr) Multivariable Analysis Sex P = Male ± 8.8 Female ± 9.5 Sie P = Right ± 9.2 Left ± 9.7 Severity of evelopmental ysplasia of hip Per center-ege angle P < Mil (>15 ) ± 8.9 Moerate (5-15 ) ± 10.1 Severe (<5 ) ± 8.2 Per acetabular inclination P = Mil (10-20 ) ± 8.7 Moerate (21-30 ) ± 9.7 Severe (>30 ) ± 9.5 UCLA score P < (minimal activity) ± (moerate activity) ± (high activity) ± 8.9 BMI P = >30 kg/m ± kg/m ± 8.5 Prior hip treatment P = No ± 9.6 Yes ± 9.0 *Raw number of all hips available for univariable analysis. Multivariable analysis base on 708 hips with complete emographic an raiographic ata. correlate with the age at surgery, with the specific goal of etermining whether symptom uration was associate with an oler age at surgery. Statistical Analysis Spearman correlations, Stuent t tests, an analysis of variance (ANOVA) were use for univariable analysis. Age was normally istribute. However, the lateral center-ege angle, anterior center-ege angle, an acetabular inclination were not; therefore, Spearman rho correlations were use. Multivariable regression analysis using generalize estimating equations was applie to etermine inepenent preictors of age at PAO. Statistical analysis was performe using SPSS Statistics (version 22.0; IBM). Two-taile values of p < 0.05 were consiere significant. Results Univariable analyses were conucte using the number of hips for which the ata on the specific factor were available (Table I). The multivariable analysis inclue the 708 hips for which complete raiographic an questionnaire ata were available. Univariable analysis showe that, of the emographic factors stuie, a BMI of >30 kg/m 2 was associate with a younger age at surgery (p = 0.04). A history of hip surgery was also associate with a younger age at PAO an prove to be inepenently preictive of an earlier age at PAO on multivariable analysis (p = 0.002). Patients with a history of a treate hip conition unerwent osteotomy an average of 2.3 years earlier than those without a history of treatment TABLE II Duration of Symptoms by Category an Age at PAO Duration of Symptoms No. of Hips Mean Age at PAO an Stan. Dev. (yr) <6 mo ± mo ± yr ± yr ± 7.9 >5 yr ± 8.8

6 668 the age at surgery between patients with mil an those with moerate ysplasia (p = 0.28). Duration of Hip Pain Prior to Surgery A majority of patients escribe having ha symptoms for one to three years prior to surgery (Fig. 2). There was a tren for patients who were oler at the time of surgery reporting that they ha ha symptoms for a longer perio of time, with almost every increase in symptom-uration category associate with an increase in the average age at surgery (Table II). When we subtracte the uration of symptoms from the age at surgery, the majority of patients in this stuy group escribe symptom onset between the ages of twenty an twenty-five years. Fig. 2 Histogram illustrating the number of responses to the general question, How long i you have hip pain/symptoms prior to PAO? The number at the top of each bar is the number of responents reporting that uration of symptoms; this number is base on all available responent ata. (Table I). We i not fin a significant correlation between activity level an BMI. Activity Level an Age at Surgery Univariable an multivariable linear regression analyses confirme that the UCLA activity score was inepenently preictive of the age at PAO. With increasing activity level, patients presente at younger ages for PAO (p < 0.001). The most significant ifference was between patients who were milly or moerately active (mean age at PAO, 26.5 an 27.0 years, respectively) an those who escribe themselves as highly active (mean age at PAO, 23.4 years) (p < 0.001). There was no significant ifference in age at presentation for surgery between patients who escribe themselves as minimally active an those who were moerately active (p = 0.56). Dysplasia Severity an Age at Surgery Univariable analysis inicate that age at PAO was irectly correlate with the lateral center-ege angle (rho = 20.69, p < 0.001) an anterior center-ege angle (rho = 20.63, p < 0.001) but not with acetabular inclination (rho = 20.04, p = 0.21). Since the lateral an anterior center-ege angles showe a strong correlation with each other (rho = 0.68, p < 0.001), the lateral center-ege angle was use to efine the severity of evelopmental ysplasia of the hip as mil (>15 to 25 ), moerate (5 to 15 ), or severe (<5 ). Multivariable linear regression analysis confirme that the lateral center-ege angle was inepenently preictive of the age at surgery (p < 0.001). Severe ysplasia was associate with a younger age at surgery. There was a significant ifference between hips with mil or moerate ysplasia an those with severe ysplasia, with mean ages at surgery of 26.0 an 26.9 years versus 22.8 years, respectively (p < 0.001). There was no significant ifference in Relationship of Activity Level an Dysplasia Severity with Age at Surgery The most significant ecreases in age at surgery for symptomatic hip ysplasia were for highly active patients with severe hip ysplasia. To evaluate the relationship between ysplasia severity an activity level, we compare four groups: (1) mil or moerate ysplasia an minimal or moerate activity, (2) mil or moerate ysplasia an a high activity level, (3) severe ysplasia an minimal or moerate activity, an (4) severe ysplasia an a high activity level (Fig. 3). Patients in Groups 2 an 3 presente for surgery at a significantly younger age than patients in Group 1. Patients in Group 4 presente at a significantly younger age than those in Groups 1, 2, an 3 (Fig. 3). Fig. 3 Histogram comparing the average ages at PAO, with stanar error bars, across four groups base on the patient s activity level an severity of evelopmental ysplasia of the hip. Group 1 = minimally or moerately active patients with mil or moerate ysplasia, Group 2 = highly active patients with mil or moerate ysplasia, Group 3 = minimally or moerately active patients with severe ysplasia, an Group 4 = highly active patients with severe ysplasia. Liste towar the bottom of each histogram bar are the average ages at the PAO an number of patients in the specific group. *Inicates that the average age at the PAO was significantly lower in Groups 2 an 3 compare with Group 1. **Inicates that the average age at the PAO in Group 4 was significantly lower compare with Groups 1, 2, an 3. UCLA = UCLA activity score, an LCE = lateral center-ege angle.

7 669 Discussion Highly active patients with more severe hip ysplasia presente for PAO at younger ages. The largest number of patients experience hip pain between one an three years prior to treatment. On average, the majority of patients in this stuy reporte that their symptoms began between the ages of twenty an twenty-five years. Aitionally, if a patient ha a known hip conition prior to PAO, they presente for surgery at an average of 2.3 years earlier than those who i not. Activity level has been evaluate as a contributor to hip arthritis in population-base stuies. Schmitt et al. foun a slightly increase risk of early hip arthrosis in former elite marathon runners 36. The UCLA activity score was utilize in the current stuy to assess physical activity. We foun that, in this younger patient population with hip ysplasia, increase activity was irectly associate with earlier presentation for hippreserving surgery. Moreover, patients who escribe themselves as highly active presente at a significantly younger age than those who were minimally or moerately active in their aily lives. While the current stuy oes not allow us to efinitively state that ecreasing activity level will change the rate at which a ysplastic hip becomes arthritic, this stuy of more than 700 cases of hip ysplasia reveale that patients with a highly active lifestyle (as etermine by UCLA scoring criteria) evelope pain an presente for treatment at significantly younger ages than less active patients with hip ysplasia of similar severity. It seems intuitive that more severe ysplasia woul place a hip at higher risk for early arthrosis. Several prior stuies have shown an association between increasing severity of hip ysplasia an a younger age at the time of presentation for arthroplasty for en-stage hip arthritis 9,11,37. In two separate large cohort stuies, Jacobsen an Sonne-Holm 9 an Jingushi et al. 38 reporte that more severe ysplasia le to an increase prevalence an earlier presentation of hip osteoarthritis an hip arthroplasty. We foun the same relationship i.e., a clear association between severity of ysplasia an age at surgery in a younger patient population seeking hip-preservation surgery (PAO). The most significant ecrease in age was seen in the patients with severe hip ysplasia (Table I), who presente for PAO at an average age of 22.8 years, compare with patients with mil or moerate ysplasia, who presente for surgery at average ages of 26.0 an 26.9 years, respectively. There was no significant ifference in age at surgery between the group with mil ysplasia an the group with moerate ysplasia. Although there are several possible reasons for this, this fining means that the hypothesis that moerately an severely ysplastic hips are more unstable than hips with mil ysplasia is only partially corroborate by our ata. Also, ue to the ifficulty with clinical measurement, we were not able to accurately assess hip stability to corroborate this hypothesis. After fining that activity level an severity of ysplasia were inepenently associate with age at surgery, we sought to etermine whether there was a efinable relationship among the three factors (Fig. 3). The patients with the highest level of activity (UCLA score of 8, 9, or 10) an those with severe ysplasia (lateral center-ege angle of <5 ) ha the youngest ages when they presente for surgery, an average of four years younger than those in the other subgroups for each variable. We stuie the various combinations of these two variables, which to our knowlege has not been one before in this population to this egree. The combination of severe ysplasia an a high activity level seeme to have the greatest effect, causing patients to present for surgery at an average of seven years earlier (at an average age of twenty-one years) than patients who were minimally or moerately active an ha mil to moerate amounts of hip ysplasia (twenty-eight years) (Fig. 3). Other factors have also been associate with an increase risk of en-stage osteoarthritis. In the Melbourne Collaborative Cohort Stuy of more than 38,000 people, Wang et al. foun that those with an increase BMI ha an increase risk of total hip replacement 39. Our univariable analysis emonstrate similar results with respect to PAO. However, the multivariable regression analysis faile to prove that BMI ha a significant, inepenent effect on the age at surgery. Therefore, while BMI ha an effect, it i not reach significance when the aforementione factors of ysplasia severity an activity level were taken into account. Finally, in aition to stuying the factors that moify the age at which patients with symptomatic evelopmental ysplasia of the hip present for surgery, we wante to assess whether there was a pattern with regar to how long patients ha been experiencing pain prior to surgery. The goal was to etermine whether it woul be possible to provie patients with an average age at which their type of ysplasia might begin to prouce symptoms on the basis of their level of activity. Although this was not a natural history stuy of all ysplastic hips, we evaluate more than 700 patients who varie with respect to emographic factors, amounts of ysplasia, an levels of activity an aske them how long they ha been experiencing pain. We think that questioning patients regaring their uration of symptoms is appropriate as it is ifficult to accurately an fully recor the multitue of reasons that patients o not unergo joint-preserving surgery for their ysplasia. We foun a spectrum of symptom urations, with the majority of patients noting that they experience pain for one to three years prior to unergoing joint-preserving surgery (Fig. 2). When we consiere the average age at surgery for the various groupings for uration of symptoms, there was a tren for patients who were oler at the time of surgery reporting that they ha ha symptoms for a longer perio of time. There are several limitations of this analysis. The most important is that we i not know the number of patients with asymptomatic hip ysplasia who i not become symptomatic or present for surgery. Secon, the UCLA score recors activity level over the previous six months, not an average over the lifetime of the hip. It is ifficult to etermine how activity levels at younger ages may have contribute to the current activity level. Also, we i not assess osteoarthritis raiographically in this stuy. This was because of the poor correlation between raiographic appearance an symptoms an the typically poor interobserver reliability of raiographic assessment of osteoarthritis 27,40. Finally, we cannot say whether moification of

8 670 weight an/or activity level will impact the evelopment of osteoarthritis. We can only state that people who ha a higher activity level an more severe ysplasia seeme to evelop pain an unergo surgery at a younger age. More patients are both learning about the etiology of their hip pain when it starts an choosing to unergo joint-preserving surgery. Given multiple reports of goo-to-excellent mi-term to long-term outcomes in the majority of patients, an the fact that the average uration of hospitalization has ecrease to three to four ays from a week, more surgeons are consiering hip-preservation surgery a viable option instea of asking patients to change their lifestyle, stop any substantial activity, an await hip replacement. Results from this stuy confirm previous beliefs that increase ysplasia severity an activity level may lea to painful arthrosis at a younger age an therefore coul be utilize to avise patients who are consiering activity moification an the timing of hip-preservation surgery. n NOTE: The authors acknowlege Dr. Etienne Belzile an Dr. Wubhav Sankar for their contributions to the final eiting of this text. Travis Matheney, MD 1 Ira Zaltz, MD 2 Young-Jo Kim, MD, PhD 1 Perry Schoenecker, MD 3 Michael Millis, MD 1 Davi Poeszwa, MD 4 Davi Zurakowski, PhD 1 Paul Beaulé, MD 5 John Clohisy, MD 6 1 Boston Chilren s Hospital, Boston, Massachusetts 2 Oaklan Orthopaeic Surgeons, Royal Oak, Michigan 3 St. Louis Chilren s Hospital, St. Louis, Missouri 4 Texas Scottish Rite Hospital for Chilren, Dallas, Texas 5 Department of Surgery, University of Ottawa, Ottawa, Ontario, Canaa 6 Washington University in St. Louis, St. Louis, Missouri aress for T. Matheney: Travis.matheney@chilrens.harvar.eu References 1. Harris WH. Etiology of osteoarthritis of the hip. Clin Orthop Relat Res Dec;213: Aronson J. Osteoarthritis of the young ault hip: etiology an treatment. Instr Course Lect. 1986;35: Murray RO. The aetiology of primary osteoarthritis of the hip. Br J Raiol Nov;38(455): Ganz R, Leunig M, Leunig-Ganz K, Harris WH. The etiology of osteoarthritis of the hip: an integrate mechanical concept. Clin Orthop Relat Res Feb;466(2): Epub 2008 Jan Ganhi R, Wasserstein D, Razak F, Davey JR, Mahome NN. BMI inepenently preicts younger age at hip an knee replacement. Obesity (Silver Spring) Dec;18(12): Epub 2010 Apr Changulani M, Kalairajah Y, Peel T, Fiel RE. The relationship between obesity an the age at which hip an knee replacement is unertaken. J Bone Joint Surg Br Mar;90(3): Harris-Hayes M, Royer NK. Relationship of acetabular ysplasia an femoroacetabular impingement to hip osteoarthritis: a focuse review. PM R Nov;3(11): e1. 8. Jacobsen S, Sonne-Holm S. Increase boy mass inex is a preisposition for treatment by total hip replacement. Int Orthop Aug;29(4): Epub 2005 Apr Jacobsen S, Sonne-Holm S. Hip ysplasia: a significant risk factor for the evelopment of hip osteoarthritis. A cross-sectional survey. Rheumatology (Oxfor) Feb;44(2): Epub 2004 Oct Jacobsen S, Sonne-Holm S, Søballe K, Gebuhr P, Lun B. Hip ysplasia an osteoarthrosis: a survey of 4151 subjects from the Osteoarthrosis Substuy of the Copenhagen City Heart Stuy. Acta Orthop Apr;76(2): Juhakoski R, Heliövaara M, Impivaara O, Kröger H, Knekt P, Lauren H, Arokoski JP. Risk factors for the evelopment of hip osteoarthritis: a population-base prospective stuy. Rheumatology (Oxfor) Jan;48(1): Kerkhoffs GM, Servien E, Dunn W, Dahm D, Bramer JA, Haverkamp D. The influence of obesity on the complication rate an outcome of total knee arthroplasty: a meta-analysis an systematic literature review. J Bone Joint Surg Am Oct 17;94(20): Liu B, Balkwill A, Banks E, Cooper C, Green J, Beral V. Relationship of height, weight an boy mass inex to the risk of hip an knee replacements in mile-age women. Rheumatology (Oxfor) May;46(5): Epub 2007 Feb Marti B, Knobloch M, Tschopp A, Jucker A, Howal H. Is excessive running preictive of egenerative hip isease? Controlle stuy of former elite athletes. BMJ Jul 8;299(6691): Clohisy JC, Barrett SE, Goron JE, Delgao ED, Schoenecker PL. Periacetabular osteotomy for the treatment of severe acetabular ysplasia. J Bone Joint Surg Am Feb;87(2): Clohisy JC, Schutz AL, St John L, Schoenecker PL, Wright RW. Periacetabular osteotomy: a systematic literature review. Clin Orthop Relat Res Aug;467 (8): Epub 2009 Apr Matheney T, Kim YJ, Zurakowski D, Matero C, Millis M. Intermeiate to long-term results following the Bernese periacetabular osteotomy an preictors of clinical outcome. J Bone Joint Surg Am Sep;91(9): Epub 2009 Sep Murphy SB, Millis MB, Hall JE. Surgical correction of acetabular ysplasia in the ault. A Boston experience. Clin Orthop Relat Res Jun;363: Peters CL, Fukushima BW, Park TK, Coleman SS, Dunn HK. Triple innominate osteotomy in young aults for the treatment of acetabular ysplasia: a 9-year followup stuy. Orthopeics Jun;24(6): Siebenrock KA, Leunig M, Ganz R. Periacetabular osteotomy: the Bernese experience. Instr Course Lect. 2001;50: Steppacher SD, Tannast M, Ganz R, Siebenrock KA. Mean 20-year followup of Bernese periacetabular osteotomy. Clin Orthop Relat Res Jul;466(7): Epub 2008 May Trousale RT, Cabanela ME. Lessons learne after more than 250 periacetabular osteotomies. Acta Orthop Scan Apr;74(2): van Hellemont GG, Sonnevel H, Schreuer MH, Kooijman MA, e Kleuver M. Triple osteotomy of the pelvis for acetabular ysplasia: results at a mean follow-up of 15 years. J Bone Joint Surg Br Jul;87(7): Wiberg G. The anatomy an roentgenographic appearance of a normal hip joint. Acta Chir Scan. 1939;83: Lequesne M; e Sèze. [False profile of the pelvis. A new raiographic incience for the stuy of the hip. Its use in ysplasias an ifferent coxopathies]. Rev Rhum Mal Osteoartic Dec;28: French. 26. Tönnis D. Normal values of the hip joint for the evaluation of X-rays in chilren an aults. Clin Orthop Relat Res Sep;119: Carlisle JC, Zebala LP, Shia DS, Hunt D, Morgan PM, Prather H, Wright RW, Steger-May K, Clohisy JC. Reliability of various observers in etermining common raiographic parameters of ault hip structural anatomy. Iowa Orthop J. 2011;31:52-8.

9 Cunningham T, Jessel R, Zurakowski D, Millis MB, Kim YJ. Delaye gaoliniumenhance magnetic resonance imaging of cartilage to preict early failure of Bernese periacetabular osteotomy for hip ysplasia. J Bone Joint Surg Am Jul;88(7): Epub 2006 Jul Auleley GR, Duche A, Drape JL, Dougaos M, Ravau P. Measurement of joint space with in hip osteoarthritis: influence of joint positioning an raiographic proceure. Rheumatology (Oxfor) Apr;40(4): Delaunay S, Dussault RG, Kaplan PA, Alfor BA. Raiographic measurements of ysplastic ault hips. Skeletal Raiol Feb;26(2): Maheu E, Caet C, Marty M, Dougaos M, Ghabri S, Kerloch I, Mazières B, Spector TD, Vignon E, Lequesne MG. Reproucibility an sensitivity to change of various methos to measure joint space with in osteoarthritis of the hip: a ouble reaing of three ifferent raiographic views taken with a three-year interval. Arthritis Res Ther. 2005;7(6):R Epub 2005 Oct Rosen A, Gamble JG, Vallier H, Bloch D, Smith L, Rinsky LA. Analysis of raiographic measurements as prognostic inicators of treatment success in patients with evelopmental ysplasia of the hip. J Peiatr Orthop B Apr;8(2): Wiig O, Terjesen T, Svenningsen S. Inter-observer reliability of raiographic classifications an measurements in the assessment of Perthes isease. Acta Orthop Scan Oct;73(5): Tönnis D. [The prearthrotic eformity as origin of coxarthrosis. Raiographic measurements an their value in the prognosis]. Z Orthop Ihre Grenzgeb Aug;116(4): Naal FD, Impellizzeri FM, von Eisenhart-Rothe R, Mannion AF, Leunig M. Reproucibility, valiity, an responsiveness of the hip outcome score in patients with en-stage hip osteoarthritis. Arthritis Care Res (Hoboken) Nov;64(11): Epub 2012 Jun Schmitt H, Brocai DR, Lukoschek M. High prevalence of hip arthrosis in former elite javelin throwers an high jumpers: 41 athletes examine more than 10 years after retirement from competitive sports. Acta Orthop Scan Feb;75(1): Murphy SB, Ganz R, Müller ME. The prognosis in untreate ysplasia of the hip. A stuy of raiographic factors that preict the outcome. J Bone Joint Surg Am Jul;77(7): Jingushi S, Ohfuji S, Sofue M, Hirota Y, Itoman M, Matsumoto T, Hamaa Y, Shino H, Takatori Y, Yamaa H, Yasunaga Y, Ito H, Mori S, Owan I, Fujii G, Ohashi H, Iwamoto Y, Miyanishi K, Iga T, Takahira N, Sugimori T, Sugiyama H, Okano K, Karita T, Ano K, Hamaki T, Hirayama T, Iwata K, Nakasone S, Matsuura M, Mawatari T. Osteoarthritis hip joints in Japan: involvement of acetabular ysplasia. J Orthop Sci Mar;16(2): Epub 2011 Feb Wang Y, Wluka AE, Simpson JA, Giles GG, Graves SE, e Steiger RN, Cicuttini FM. Boy weight at early an mile aulthoo, weight gain an persistent overweight from early aulthoo are preictors of the risk of total knee an hip replacement for osteoarthritis. Rheumatology (Oxfor) Jun;52(6): Epub 2013 Jan Clohisy JC, Carlisle JC, Trousale R, Kim YJ, Beaule PE, Morgan P, Steger-May K, Schoenecker PL, Millis M. Raiographic evaluation of the hip has limite reliability. Clin Orthop Relat Res Mar;467(3): Epub 2008 Dec 2.