historically , the treatment of patellar fractures has undergone many changes in operative methods [ 1 , 4 , 5 , 7 ] . in the 1950s , the principle of using a modified tension band technique for treatment of patellar fractures was first proposed and then subsequently recommended as the primary treatment method for patellar fractures [ 5 , 6 , 15 ] . the principle of the tension band technique is to convert the tension forces acting on the anterior surface into compression forces at the articular surface . this technique can substantially improve results because of its reliable fixation and allowance of early joint motion . first , the tension band is supplemented by longitudinal smooth kirschner wires ( k - wires ) that bear the risk of loosening and migration [ 8 , 15 ] . second , direct interfracture compression can not be achieved with the k - wire , and additionally , there is the potential of skin irritation [ 3 , 5 , 13 ] . we have adopted what we perceive to be an improved technique , the titanium cable - cannulated screw tension band construct , to remedy the shortcomings of the modified k - wire tension band in treating patellar fractures . we compared the titanium cable - cannulated screw tension band technique with the modified tension band technique to see whether the new technique could ( 1 ) achieve better reduction and direct interfragmentary compression force ; ( 2 ) shorten fracture healing time ; ( 3 ) decrease complications , such as loosening of implants and skin irritations ; and ( 4 ) achieve better knee function . this retrospective study included 101 patients ( 48 men , 53 women ) aged 22 to 85  years ( mean , 56.6  years ) operated on between january 2006 and june 2009 . from january 2006 to december 2006 , all patients were treated with the modified tension band method . from january 2007 to june 2009 , we introduced the titanium cable - cannulated tension band technique . patient selection was influenced by cost as the titanium cable - cannulated technique was offered only to patients who agreed to pay for this higher - cost procedure . all injuries were enclosed and included slip and fall accidents ( 94 patients ) and car accidents ( seven patients ) . operations were considered when the articular displacement was greater than 2  mm or fragment separation was greater than 3  mm on radiography . the time from fracture to the operation was 1 to 7  days ( mean , 3  days ) . the inclusion criteria were ( 1 ) ao / ota   34-c1 fractures , ie , patellar fractures primarily with a transverse fracture line ; and ( 2 ) ao / ota 34-c2 fractures , ie , transverse fractures with a single additional fragment created by a longitudinal fracture line . patients were divided into either a titanium cable - cannulated screw tension band group or a modified k - wire tension band group , according to their operation . there were 49 patients in the titanium cable - cannulated screw tension band group ( 19 men , 30 women ) with a mean age of 57.12  years ( range , 2283  years ) , and there were 52 patients in the k - wire tension band group ( 29 men , 23 women ) with a mean age of 56.12  years ( range , 2682  years ) . univariate t tests indicated there were no differences in age , gender , mechanism of injury , fracture classification , and interfragmentary gap between the two groups ( table  1 ) . followup was at least 1  year ( range , 13  years).table  1differences between the two groupsvariablemodified kirschner wire tension bandtitanium cable - cannulated screw tension bandchi square / t valuep valueage ( years)*56.12    16.6457.12    15.000.3190.75gender  male29192.920.087  female2330injury reason  slip and fall48460.2850.593  car accident43ao / ota classification  34-c139292.8690.09  34-c21320interfragmentary gap ( mm)*15.85    7.9516.78    5.370.6840.495 *  values are expressed as mean    sd ; the remaining values are expressed as number of patients . differences between the two groups *  values are expressed as mean    sd ; the remaining values are expressed as number of patients . after sectioning the skin and subcutaneous tissue followed by fully exposing the patella and its sides , we confirmed the quadriceps femoris aponeurosis and the ligament patellae were adherent to the patellar surface . we examined the fracture and condition of the bilateral aponeuroses and joint capsule , removed fracture chips or any intraarticular hematoma , and rinsed the articular cavity . in the ao / ota 34c2 fractures , the longitudinal fracture was fixed by one lag screw inserted perpendicularly to the fracture line . with the knee in extension , we clamped the fragments to reduce the fracture with a large towel clamp . after we observed the reduction of articular surface under intraoperative fluoroscopy , we drilled two k - wires ( 2.0-mm diameter ) in parallel from the lower pole to the superior pole of the patella , with a 2-cm space and a 5- to 10-mm distance from the patellar articular surface . the position of the k - wire was determined using intraoperative fluoroscopy . in the modified tension band group , we bent the upper end of the k - wire into hooks and threaded a 1.2-mm steel wire through the upper hooks and lower end of the k - wire to form a figure - of - eight tension band . we then tightened the steel wire using a wire cutter , hid the upper hooks of the k - wires in the patella , and reobserved reduction of the articular surface by intraoperative fluoroscopy . if the reduction was satisfactory , we cut off the tails of the k - wires and the steel wire . in the titanium cable - cannulated screw tension band group , one k - wire was first removed and a cannulated screw guide pin was inserted along the pin tract . we drilled along the guide wire with a cannulated bit and , after measuring its depth , screwed a 4.0-mm titanium cannulated compression screw ( synthes inc , west chester , pa , usa ) along the guide wire . the screw head remained proud of the patella cortex , and the proximal end of the screw should be close to , or embedded within , the patella . we removed the guide wire and threaded a 1.3-mm - diameter titanium cable ( consisting of a total of nine strands ; zimmer inc , warsaw , in , usa ) through each of the cannulated screws . we then tightened the titanium cable anterior to the patella to form the tension band , fixed the titanium cable with cable clamps , and cut off the excessive titanium cable ( fig . 1a  cthe tension band fixation technique using titanium cables and cannulated screws is shown . ( a ) two 2.0-mm - diameter k - wires are drilled from the lower pole to the superior pole of the patella after reducing the fracture . ( b ) two 4.0-mm - diameter cannulated screws are screwed along the guide wire . ( c ) titanium cables are threaded through the cannulated screws and tightened anterior to the patella . ( a ) two 2.0-mm - diameter k - wires are drilled from the lower pole to the superior pole of the patella after reducing the fracture . ( b ) two 4.0-mm - diameter cannulated screws are screwed along the guide wire . ( c ) titanium cables are threaded through the cannulated screws and tightened anterior to the patella . patients performed quadriceps femoris contraction exercises soon after the operation , passive joint flexion and extension exercises 2  days after the operation , and active joint flexion and extension exercises 7  days after the operation . one month later , patients were permitted to perform partial - weightbearing walking , and conventional radiographs were obtained , including lateral and ap patellar radiographs . patients were reexamined at 1 , 2 , 3 , 6 , and 12  months after the operation to observe the fracture healing . fracture healing was defined as when a patient had no local pain or tenderness , the ability to walk well without help , and evidence of trabecular bone growing across the fracture line . one year after surgery , the knee function was evaluated according to the iowa knee score criteria , which evaluates knee function in daily life , inquires about joint pain when weightbearing , walking gait , the existence of deformity or instability , and joint rom . the total score is 100 points : 90 to 100 points is excellent , 80 to 89 points is good , 70 to 79 points is fair , and less than 70 points is poor . results were analyzed by spss statistical software ( spss inc , chicago , il , usa ) . the differences in internal fixation fracture healing time , knee function , and incidence of complications between the two groups were analyzed using univariate analysis . logistic regression was used to determine whether gender , age , injury mechanisms , and fracture classifications had an influence on differences between the two operation methods in terms of the postoperative interfragmentary gap , fracture healing time , complications , and knee function . the logistic regression determining which of the variables remained significant as they relate to the others was considered significantly different when p  <  0.05 . there was no difference ( p  <  0.05 ) in the operation time between the k - wire tension band group ( mean , 48 minutes ; range , 4060 minutes ) and cable - cannulated screw tension band group ( mean , 55 minutes ; range , 4570 minutes ) . five patients in the k - wire tension band group experienced skin irritation generated by wire tails after the operation ; eight patients had k - wire tension band loosening and migration , and in five of these , the fracture healed with the protection of a brace and the internal fixation was removed 1  year later . three patients with internal fixation loosening and fracture displacement required a second operation , which was performed directly after the fracture displacement was discovered ( fig .  2 ) . in the cable - cannulated screw tension band group , no complications were observed after the operations . 2a  da 34-year - old woman with a patellar fracture had k - wire tension band fixation failure . ( a ) a lateral radiograph shows the transverse patellar fracture 1  month after k - wire tension band fixation with tension band loosening . ( b ) a lateral radiograph taken 2  months postoperatively shows the fracture has not healed . ( c ) a lateral radiograph shows the patella fracture after revision with a titanium cable - cannulated screw tension band . ( d ) a lateral radiograph taken 2  months after the second operation shows fracture healing and recovery of knee function . a 34-year - old woman with a patellar fracture had k - wire tension band fixation failure . ( a ) a lateral radiograph shows the transverse patellar fracture 1  month after k - wire tension band fixation with tension band loosening . ( b ) a lateral radiograph taken 2  months postoperatively shows the fracture has not healed . ( c ) a lateral radiograph shows the patella fracture after revision with a titanium cable - cannulated screw tension band . ( d ) a lateral radiograph taken 2  months after the second operation shows fracture healing and recovery of knee function . the mean postoperative fracture spacing of the articular surface was larger ( p  =  0.001 ) in the k - wire tension band group ( 0.63  mm ; range , 03  mm ) than in the cable - cannulated screw tension band group ( 0.04  mm ; range , 02  mm ) ( table  2 ) . the postoperative interfragmentary gaps in the tension band group were 2  mm in 10 patients and 3  mm in two patients ( fig . 3 ) , whereas no patient s interfragmentary gap was greater than 2  mm in the titanium cable - cannulated screw tension band group.table  2results of the two groupsvariablesmodified kirschner wire tension bandtitanium cable - cannulated screw tension bandchi square / t valuep valuepostoperative interfragmentary gap  0  mm334716.14 < 0.001    1  mm192knee function*0.01  901003645  808994  707940    6930fracture healing time ( months)2.33    1.152.00    02.0500.046complications  04149  1100 < 0.001  210 * iowa knee score   ( total score  =  100 points ) : 90100  =  excellent ; 8089  =  good ; 7079  =  fair ;    69  =  poor ; values are expressed as mean    sd ; the remaining values are expressed as number of patients ; fisher s exact test.fig . 3a  ca 45-year - old woman with a patellar fracture was treated with k - wire tension band fixation . ( b ) a lateral radiograph taken after k - wire tension band fixation shows the fracture line with levels and gaps . results of the two groups *  iowa knee score   ( total score  =  100 points ) : 90100  =  excellent ; 8089  =  good ; 7079  =  fair ;    69  =  poor ; values are expressed as mean    sd ; the remaining values are expressed as number of patients ; fisher s exact test . a 45-year - old woman with a patellar fracture ( b ) a lateral radiograph taken after k - wire tension band fixation shows the fracture line with levels and gaps . ( c ) the mean fracture healing time was longer ( p  =  0.046 ) in the k - wire tension band group ( 2.33  months ; range , 24  months ) than in the cable - cannulated screw tension band group ( 2.00  months ) ( table  2 ) ( fig . 4a  ca 35-year - old man with a patellar fracture underwent fracture fixation with a titanium cable - cannulated screw tension band . ( b ) a lateral radiograph shows the patella fracture after titanium cable - cannulated screw tension band fixation . a 35-year - old man with a patellar fracture underwent fracture fixation with a titanium cable - cannulated screw tension band . ( b ) a lateral radiograph shows the patella fracture after titanium cable - cannulated screw tension band fixation . ( c ) a lateral radiograph taken 2  months postoperatively shows fracture healing . according to the iowa score criteria , the knee function scores were better ( p  =  0.01 ) in the titanium cable - cannulated screw tension band group ( excellent , 45 patients ; good , four ; fair and poor , none ) than in the modified k - wire tension band group ( excellent , 36 patients ; good , nine ; fair , four ; poor , three ) ( table  2 ) . logistic regression showed postoperative interfragmentary gap and knee function were associated with the operation method ( p  =  0.0001 and p  =  0.006 , respectively ) , with the cable - cannulated screw tension band group being superior . slower healing time was associated with ( p  =  0.013 ) ao / ota c2 fractures but not with ( p  =  0.997 ) the operation method . because there was no main complication in the cable - cannulated screw tension band group , the logistic regression analysis could not show a significant association with the operation method ( odds ratio  =  0.000 ) ( table  3).table  3results of logistic regression analysis*variablepostoperative interfragmentary gapcomplicationshealing timeknee functionodds ratiop valueodds ratiop valueodds ratiop valueodds ratiop valuegender ( male)1.1870.7161.1810.8181.6830.5070.8960.806age ( >  50  years)0.3980.1410.9700.1591.0050.8490.9840.263injury ( slip and fall)5.777e80.9995.6180.1320.0000.9993.5680.168ao / ota classification ( 34-c2)0.5570.3420.8210.8276.9970.0132.2530.093operation method ( modified kirschner wire tension band)17.8450.00010.0000.9970.0000.9973.3800.006 *  variables included : gender ( male , female ) ; age (   50  years ,  >  50  years ) , injury ( slip and fall , car accident ) , ao / ota classification ( 34-c1 , 34-c2 ) , operation method ( titanium cable - cannulated screw tension band , modified k - wire tension band ) , postoperative interfragmentary gap ( 0  mm ,    1  mm ) , complications ( loosening of implant , failure of fixation , skin irritation ) , healing time (   2  months ,  >  2  months ) , knee function ( excellent , less than excellent ) . results of logistic regression analysis * *  variables included : gender ( male , female ) ; age (   50  years ,  >  50  years ) , injury ( slip and fall , car accident ) , ao / ota classification ( 34-c1 , 34-c2 ) , operation method ( titanium cable - cannulated screw tension band , modified k - wire tension band ) , postoperative interfragmentary gap ( 0  mm ,    1  mm ) , complications ( loosening of implant , failure of fixation , skin irritation ) , healing time (   2  months ,  >  2  months ) , knee function ( excellent , less than excellent ) . selecting the appropriate and effective method and materials for treating patellar fractures is a tough challenge for orthopaedists [ 1 , 68 , 12 , 13 , 15 ] . although the modified tension band technique ( eg , tension band supplemented by longitudinal k - wires ) has long been the mainstay for fixation of transverse fractures of the patella [ 1 , 46 , 8 , 13 , 14 ] , it is not without shortcomings . we therefore compared an alternative operative method , the titanium cable - cannulated screw tension band technique , with the modified tension band technique to see whether this technique could ( 1 ) achieve better reduction and direct interfragmentary compression force ; ( 2 ) shorten fracture healing time ; ( 3 ) decrease complications , such as loosening of implants and skin irritations ; and ( 4 ) achieve better knee function . first , the decision to treat patients with either a modified tension band or titanium cable - cannulated screw tension band was subject to selection bias as this was not a randomized study . second , the degree to which the titanium cable or the steel wire was tightened was not standardized . as such , we could not be sure that the tension was equal in any of the patients , which might have had an influence on the interfragmentary pressure and tension band force . finally , 12 patients were lost to followup , which might have influenced the final result . the cable - cannulated screw tension band was better than the modified k - wire tension band in fracture reduction . in the modified tension band group , the postoperative interfragmentary gaps were 2  mm in 10 patients and 3  mm in two patients after surgery , whereas no patient s interfragmentary gap was greater than 2  mm in the titanium cable - cannulated screw tension band group . as the support of a tension band , the k - wire itself can not generate reduction and compression effects on fractured bones . rather , the reduction and compression effects on the patellar fracture line are generated by tightening the wires from the superior pole to the lower pole [ 1 , 4 , 15 ] . however , the flexibility of k - wires will counteract a part of the force that should act on the fractured bone . when using a cable - cannulated screw tension band the primary pressure is achieved by the two cannulated lag screws   and the titanium cable , which is fixed through the cannulated screw and tightened and plays its role as a tension band . because the acting force generated by the cannulated screws is perpendicular to the fracture [ 2 , 9 , 14 ] , the acting forces on the patellar articular and anterior surfaces are consistent , which is different from a modified k - wire tension band ( fig . 5a  bthe schematic diagrams illustrate titanium cable - cannulated screw tension band fixation of a patellar fracture . ( a ) the cannulated screw is located near the leading edge of the patella . ( b ) the cannulated screw is located away from the leading edge of the patella . regardless of the position of the cannulated screw , the titanium cable is close to the surface of the patella . the schematic diagrams illustrate titanium cable - cannulated screw tension band fixation of a patellar fracture . ( a ) the cannulated screw is located near the leading edge of the patella . ( b ) the cannulated screw is located away from the leading edge of the patella . regardless of the position of the cannulated screw , the titanium cable is close to the surface of the patella . loosening of the implant is considered the main complication of patellar fracture fixation . in our study , eight patients in the modified k - wire band group had loosening of the k - wire tension band ; three of them had separation of the fracture and required a second operation . loss of fixation has been reported to occur in 0% to 20% of operatively treated patellar fractures [ 6 , 9 , 11 ] . the surface of a k - wire is smooth , so loosening of k - wire is inevitable with time . a previous study   suggested the reason for poor outcomes of a k - wire tension band was initial separation of the fracture fragments caused by properties of the wire and further separation resulting from the change in wire plasticity . secondarily , the method of bending the k - wire may influence the result . in our study some authors argue that bending of the distal wire ends decreases the risk of proximal wire migration with loss of reduction [ 8 , 11 , 13 , 15 ] . additionally , the technique used in twisting the wire may influence the stability of fixation . some authors selected to twist the wire at two sites , rather than one [ 7 , 11 ] . we twisted the wire at only one site , which might have been a cause of implant failure . some researchers use modified steel wires to increase the stability of a k - wire tension band ; however , the effect still will be reduced by the flexibility of k - wires [ 8 , 12 , 13 ] . the probability of titanium cable - cannulated screw loosening is very low owing to the dense cancellous bone of the patella and the fact that the distal end of the cannulated screw is threaded . in addition , the strong titanium cable tightly attaches to the patellar surface to limit the separation of fracture fragments as a tension band . we chose two individual tension band cables rather than one figure - of - eight band , because this allows tightening of the tension band independently . five patients experienced skin irritation in the modified k - wire tension band group , whereas no patients in the cable - cannulated screw tension band group had skin irritation . in some studies , symptoms attributable to wire irritation necessitated removal in approximately 15% of the cases [ 6 , 11 ] . k wire prominence and migration are the primary causes of skin irritation associated with this technique [ 7 , 13 ] . with the cable - cannulated screw tension band technique , the tail of the cannulated screw tightly attaches at the superior or inferior pole of the patella , and the screw threads are not exposed to the patellar surface ; also , the diameter of the titanium cable is only 1.3  mm , and it closely attaches to the patellar surface after being tightened reducing the risk of skin irritation and postoperative activity discomfort . the iowa knee score was better in the cable - cannulated screw tension band group . according to the logistic regression analysis , the healing time was associated with fracture classification , suggesting complicated fractures needed longer healing time , independent of the operative method . with respect to removal of the internal fixation , generally k - wires should be removed 1  year after surgery except when patients refuse , whereas the cables and cannulated screws , both being titanium , rarely produce adverse effects such as skin irritation . however , removal of the titanium cannulated screws , if needed , is more difficult than a k - wire . we developed an improved technique to remedy the shortcomings of the modified k - wire tension band in treating patellar fractures . a titanium cable - cannulated screw tension band can achieve good fracture reduction and healing with a low rate of complications .
backgroundalthough the modified tension band technique ( eg , tension band supplemented by longitudinal kirschner wires ) has long been the mainstay for fixation of transverse fractures of the patella , it has shortcomings , such as bad reduction , loosening of implants , and skin irritation.questions/purposeswe conducted a retrospective comparison of the modified tension band technique and the titanium cable - cannulated screw tension band technique.patients and methodswe retrospectively reviewed 101 patients aged 22 to 85  years ( mean , 56.6  years ) with ao / ota 34-c1 fractures ( n  =  68 ) and 34-c2 fractures ( n  =  33 ) . fifty - two patients were in the modified tension band group and 49 were in the titanium cable - cannulated screw tension band group . 
 followup was at least 1  year ( range , 13  years ) . 
 comparison criteria were fracture reduction , fracture healing time , and the iowa score for knee function.resultsthe titanium cable - cannulated screw tension band group showed improved fracture reduction , reduced healing time , and better iowa score , compared with the modified tension band group . in the modified tension band group , eight patients experienced wire migration , three of these requiring a second operation . 
 there were no complications in the titanium cable - cannulated screw tension band group.conclusionsthe titanium cable - cannulated screw tension band technique showed superior results and should be considered as an alternative method for treatment of transverse patellar fractures.level of evidencelevel iii , therapeutic study . 
 see the guidelines for authors for a complete description of levels of evidence .