Postinfective physel rs MRI fetures nd choice of mngement Murry Hyes, MB ChB Svvs Andronikou, MB BCh, FC Rd, FRCR, PhD Crey Mckenzie, MB ChB, FCRd Jco du Plessis, MB ChB Reen George, MB BS, MMed Rd Slomine Theron, MB ChB, MMed Rd, FCRd Deprtment of Rdiology, University of Stellenosch, Tygererg Astrct We present series of 6 ptients with physel rs s result of infection (predominntly meningococcl) demonstrting the typicl MRI fetures of this entity nd n explntion of how these fetures ffect the choice of mngement. Aim Our im is to demonstrte ny distinctive mgnetic resonnce imging (MRI) fetures of postinfective physel rs cused y meningococcl nd other infections nd show how these fetures help the surgeon in selecting the est mngement option. Introduction There re vrious cuses of growth-plte injuries nd while trum is the most common, infection (e.g. meningococcemi) hs lso een known to cuse significnt injuries. Growth-plte injury is common nd cn result in lifelong disility with suset of physel injuries resulting in premture growth rrest due to ony ridge formtion cross the physis. 1 Also known s physel rs, these re focl defects in the physis with resulting ony continuity etween the epiphysis nd metphysis. 2 These ridges usully form 1-2 months post injury ut only 2% of ptients with growth-plte injuries develop physel dmge tht is cliniclly significnt. 3,4 Physel rs result in either ngulr deformities or leg-length discrepncies. 2,4 MRI hs een shown to e useful in the evlution of physel rs. 2 Meningococcemi my hve profound effect on the skeletl system of growing child nd survivors re t high risk of developing permnent effects. 5 Nine ptients with physel rs s result of meningococcemi hve een reported ut no MRI fetures hve een descried Fig. 1. Post-trumtic physel r due to Slter Hrris IV frcture T1 weighted () nd grdient echo () sequences demonstrte continuous r s well s the frcture line in oth the metphysis nd epiphysis. The distl femur is common site for post-trumtic physel rs. The physis is regulr, however, nd the epiphysis is not significntly distorted. 44 SA JOURNAL OF RADIOLOGY Septemer 2007
Fig. 2. Postmeningococcl physel r. () This grdient echo sequence demonstrtes distl tiil physel r tht is centrl nd results in tenting deformity of the epiphysis. () A sgittl imge in the sme ptient shows the distl nd proximl tiil physes reveling second r t the nterior portion of the proximl tiil physis. for these. 5 We im in this pper to descrie the MRI fetures of physel rs which re the result of meningococcemi nd other infections, nd to show how these fetures help with mngement decisions. Method A retrospective nlysis of series of ptients referred for evlution of physes with postinfective leg-length discrepncies (meningococcemi in 5 of the 6 ptients, the sixth hving hd neontl sepsis with no custive orgnism documented). The following fetures were evluted sed on fetures lredy descried in the literture: Numer of sites involved Percentge of physis involved Presence of flme-shped protrusions of crtilge (the physel line is displced into metphysis or epiphysis in flme shpe) Irregulrity of physis (irregulrity eyond the norml corrugted mrgin more like n ECG trce) Distortion of epiphysis (the shpe nd/or size of physis is ltered). The percentge of physis involved ws clculted y dividing the physis into sgittl nd coronl segments which were then trnsposed s grid onto n xil mp of the physis. The numer of involved segments ws then clculted nd when compred with the totl numer of segments percentge of involvement ws clculted. Figs 1-6 demonstrte vrious fetures encountered. Results Of the 6 ptients evluted, 2 hd multiple sites involved with totl of 13 physel rs. Overll 4 of the 13 rs showed involvement of 50% or more of the physis. The vst mjority of postinfectious physel rs evluted showed flme-shped protrusions s well s physel irregulrity nd epiphysel distortion (Tles I nd II). In comprison the trum group hd no rs involving 50% or more of the physis, only two-thirds showed physel irregulrity nd less thn hlf showed physel distortion. Tle I. Distriution of physis involvement nd etiologies Percentge of physis involved Trum Infection <33% 5 7 >33% ut <50% 4 1 +/- 50% 0 3 >50% ut <66% 0 0 >66% ut <100% 0 1 100% 0 0 Discussion The different etiologies of physel rs presumly ffect the physis in different wys, which in turn ffects mngement. Any insult to the physis cn result in physel r. 2 The most common cuse of physel r is 45 SA JOURNAL OF RADIOLOGY Septemer 2007
Tle II. Distriution of fetures Fetures of physel rs Trum Infection Continuity through physis 7 10 Flme-shped protrusions 7 9 Irregulrity of physis 6 10 Distorted epiphysis 4 10 frcture/trum. Other insults to the physis with formtion of physel r include infection, rdition, tumours, therml injury, vsculr injury nd corticosteroid therpy, nd some re considered idiopthic. 1-3, 6 Meningococcemi (due to infection with Neisseri meningitidis) results in diffuse vsculitis, thromosis, hemorrhge nd necrosis which lso involves the growth pltes, resulting in vrile permnent ischemic dmge. 5 As result, ony ridges develop. 5 The centrl prt of the physis hs een shown to e vulnerle nd is often involved in meningococcl insults. 7 Once physel r hs developed, imging needs to evlute size nd loction of the physel r s well s the severity of growth disturnce efore decisions on mngement cn e tken. 6 Historiclly dignosis hs een mde using plin rdiogrphy, conventionl tomogrphy, computed tomogrphy (CT) nd scintigrphy. 1,4 MRI hs een shown to e more ccurte thn conventionl techniques 2 s it hs multiplnr cpilities llowing for cross-referencing of imges in two plnes 2,8,6 nd fcilitting mpping. 8,6 MRI hs excellent contrst nd sptil resolution. 2 MRI lso hs the dvntge of detecting firous nd crtilgenous rs, shows up the crtilginous epiphysis, the ctul growth plte nd lso detects injury to the ligments, menisci nd vessels. 4,6,8,9 Becuse of these dvntges, suclinicl rs cn esily e detected y MRI, nd in ddition MRI cn chnge the Slter Hrris clssifiction in pproximtely hlf of ptients with physel trumtic injury. 4,8 This is useful for differentiting etween Slter Hrris II nd IV frctures when the distl humerus is un-ossified nd lso detects metphysel extension in Slter Hrris type III frctures reclssifying these s type IV frctures. 8 Rdiologist greement hs een etter using MRI thn using other techniques. 4 Sgittl nd coronl-plne imging diminishes the prtil-volume verging tht is inherent in imges of xilly orientted structures. 2 Spin echo T1- nd T2-weighted sequences re useful nd T1-weighted sequences re especilly useful for ssessing the tilted growth rrest nd recovery lines nd for detecting ftty mrrow in the physel r. 4,8 Grdient reclled echo (GRE) sequences re recommended y numerous uthors nd show norml physel plte crtilge hs high signl. 1-4 Certin ntomicl sites re prone to growth rrest. 1 The distl Fig. 3. Postmeningococcl physel r coronl grdient echo imge demonstrtes tht the irregulrity of the medil spect of the proximl tiil physis is result of multiple smll rs. Fig. 4. Postneontl sepsis coronl imge demonstrtes continuous physel r t the distl femur with mrked irregulrity t the lterl hlf of the physis. This is in contrst to the norml regulr proximl tiil physis. 46 SA JOURNAL OF RADIOLOGY Septemer 2007
Fig. 5. Postmeningococcl physel r. () T1-weighted coronl sequence demonstrtes oth proximl nd distl tiil physel rs. At the proximl physis there is irregulrity nd discontinuity medilly. At the distl physis continuous physel r contining ftty mrrow signl is present. () The grdient echo sequence confirms the centrl continuous r t the distl tii y showing discontinuity of the norml physel high signl. femur hs disproportiontely high incidence of growth rrest, nd this is relted to the centrl physel undultion. 1 There is lso significnt ssocition etween the cuse of growth rrest nd the ntomicl site involved. 1 Physel rs re more common in the lower thn upper extremities irrespective of the cuse. 1 Different sections of the physis re lso more likely to e involved depending on which physis is involved. At the distl tii the nterior medil section of the physis, lso known s Kump's ump, is most susceptile to growth rrest. 1 The proximl femur nd the proximl tii re more susceptile to physel rs in their periphery. 1 Our results show tht unlike rs cused y trum, those cused y infection hve the following chrcteristics: Involve more physel loctions (up to 6 in 1 ptient) nd cn e ilterl My involve tiil nd femorl loctions (proximlly nd distlly t the tii) In ddition to continuity of the epiphysis nd metphysis nd flmeshped protrusions of crtilge into the epiphysis or metphysis they my cuse irregulrity of the physis eyond the norml corrugtion nd distortion of the size or shpe of the epiphysis Commonly involve lrger surfce re of the physis (50% or greter). Current tretment for physel rs ims to prevent deformity nd correct leg-length discrepncy. 1,8 Tretment options include: Osteotomies to correct ngultion 1,2 Contrlterl physel rrest to prevent leg-length discrepncy 1,2 Shortening/lengthening procedures 2 Physel r excision to relieve growth impednce. 1,2 The rdiologist cn ssist the orthopedic surgeon with mngement choice nd help with pre-opertive plnning. Pre-opertive ssessment requires determintion of the size, loction nd contour of the r. 1-4 This helps to determine optiml surgicl exposure nd helps minimise dmge to the epiphysis. 1,2 Bridges etween 30% nd 50% of the size of the physis require excision nd interposition of ft. 2,4 Brs less thn 30% of the size of the physis cn e mnged without surgery. 4 Brs over 50% of the size of the physis require more extensive surgery. 4 Our results show tht postinfective physel rs often inolve 50% or more of the physis, which my require extensive surgery, wheres posttrumtic rs often require no surgicl intervention nd when they do, it is unlikely to e extensive. Conclusion Physel rs cused y infection, nd in prticulr meningococcemi, differ from those cused y trum. The multiple loctions involved nd the extent of involvement of the surfce re hve direct ering on prognosis nd choice of mngement (including surgery) with extent of the physis involved eing the most importnt determining fctor. 47 SA JOURNAL OF RADIOLOGY Septemer 2007
Fig. 6. Flme-shped projections of the physel crtilge into the djcent metphysis re demonstrted in oth postinfective nd post-trumtic physel injury nd re considered s fetures in keeping with physel r seen in this ptient on grdient echo () nd T1-weighted imging (). 1. Ecklund K, Jrmillo D. Ptterns of premture physel rrest: MR imging of 111 children. AJR 2002;178: 967-972. 2. Bors JJ, Peterson HA, Ehmn RL. MR imging of physel rs. Rdiology 1996; 199(3): 683-687. 3. Crig JG, Crmer KE, Cody DD, et l. Premture prtil closure nd other deformities of the growth plte: MR imging nd three dimensionl modeling. Rdiology 1999; 210(3): 835-843. 4. Lohmn M, Kivisri A, Vehms T, Kllio P, Puntil J, Kivisri L. MRI in the ssessement of growth rrest. Peditr Rdiol 2002; 32: 41-45. 5. Grogn DP, Love SM, Ogden JA, Millr EA, Johnson LO. Chondro-osseous growth normlities fter meningococcemi. J Bone Joint Surg Am 1989; 71 (6): 920-928. 6. Jrmillo D, Hoffer FA. Crtilgenous epiphysis nd growth plte: norml nd norml MR imging findings. AJR 1992;158: 1105-1110. 7. Lor T, Hrtmn AL, Jrmillo D. Locl physel widening on MR imging: n incidentl finding suggesting prior metphysel insults. Peditr Rdiol 1997; 27:654-662 8. Jrmillo D, Hoffer FA, Shpiro F, Rid F. MR imging of frctures of the growth plte. AJR 1990;155:1261-1265 9. Rogers LF, Poznnski AK. Imging of epiphysel injuries. Rdiology 1994; 191: 297-308. 48 SA JOURNAL OF RADIOLOGY Septemer 2007