The Journal of Arthroplasty Vol. 23 No. 3 2008

Less Invasive Stabilization System for theManagement of Periprosthetic Femoral Fractures

Around Hip Arthroplasty

Vijaya Kumar, MS(Orth), MRCS,* Prashant Kanabar, MS(Orth), FRCS(Orth),*P. Julian Owen, FRCS(Orth),* and Neil Rushton, MD, FRCSy

Abstract: We present a study of 18 periprosthetic femoral fractures treated with lessinvasive stabilization system between September 2001 and March 2005. Threepatients died during the follow-up period owing to unrelated causes and are excludedfrom the final results. The average age was 81.6 years, and the average follow-upperiod was 11.7 months. Twelve patients had significant comorbidities preopera-tively. The surviving 15 patients had satisfactory fracture union, although one patientrequired replating with a less invasive stabilization system plate after a fall. Onepatient developed deep infection with a chronic sinus. Three patients were noted tohave mild to moderate discomfort around the prominent implant. Key words:periprosthetic fracture, hip arthroplasty, LISS plate.© 2008 Elsevier Inc. All rights reserved.

Periprosthetic fracture is a serious but an uncom-mon complication of hip arthroplasty. The incidenceof periprosthetic fractures after total hip arthroplastyvaries in different studies from 0.1% to 6% [1].There is no consensus on the best treatment for

these injuries indicated by the use of varioustreatment methods ranging from nonoperativetreatment such as traction to internal fixationusing different implants. These patients are oftenelderly with osteoporotic bones and have signifi-cant comorbidities. In a review article, Learmonth[2] has suggested an algorithm for the manage-ment of these fractures. In Vancouver type B1fracture, he has suggested fixation of fracture with

From the *Department of Trauma and Orthopaedics, Addenbrooke'sHospital, Cambridge, UK; and yOrthopaedic Research Unit, Universityof Cambridge, Cambridge, UK.

Submitted June 15, 2006; accepted January 11, 2007.No benefits or funds were received in support of the study.Reprint requests: Vijaya Kumar, MS(Orth), MRCS, 30/11

James Street, Stirling, FK8 1UG, UK.© 2008 Elsevier Inc. All rights reserved.0883-5403/08/2303-0019$34.00/0doi:10.1016/j.arth.2007.01.028

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a plate, cables and screws, and a cortical strutgrafts. The concept of less invasive stabilizationsystem (LISS Synthes USA, Paoli, Pa) has beenbased on anatomically shaped buttress platesanchored with monocortical screws. The 2 theore-tical advantages of LISS include improved biome-chanics of fixation and less disruption to bloodsupply. The screws are locked with the plate by athread on the outer edge of the screw head and onthe inner edge of the plate hole. The angularstability between the screws and the plate nolonger requires any compression between the plateand the bone to ensure secure anchoring. Becausethere is no need for the plate to touch the bone andcan be inserted with a percutaneous technique, thedisruption of blood supply is less likely by plate'sfootprint. It is noted that, unlike traditional plates,the locked nature of the LISS plate screws requiresthat the plate fail by all of the screws pulling outtogether. This failure mode provides added struc-tural support that is thought to be particularlyimportant in osteoporotic bone [3-5]. Its ability touse unicortical screws is a potential advantage inthe presence of the femoral stem. O'Toole et al [6]

Fig. 1. A, Displaced periprosthetic fracture around hemiarthroplasty. B, Six months postoperative, radiograph showingevidence of fracture union.

Less Invasive Stabilization System � Kumar et al 447

in their study demonstrated low complication ratesthan the other historically used devises to treat femurfractures ipsilateral to hip or knee prosthesis. We haveevaluated the results of this relatively newer implantfor treatment of periprosthetic femoral fractures.

Patients and Methods

Eighteen patients with a periprosthetic femoralfracture were treated with titanium LISS platesbetween September 2001 and March 2005. Therewere 2male and 16 female patients. The average ageat the time of injury was 81.6 years (range, 63-93 years). Twelve of the patients had significantcomorbidities. One patient had also sustained anipsilateral ankle fracture. The fractures were classi-fied according to the Vancouver classification forperiprosthetic fracture of femur [7]. Our indicationsfor LISS included type B1, type C, and patients withtype B2 fractures medically unfit for revisionsurgery. Ten fractures were classified as type B1, 2as type B2, and 6 as type C. Eleven fractures werearound total hip arthroplasty (7 cemented and4 uncemented), and 7 were around hemiarthro-plasty (3 cemented and 4 uncemented). Of the7 patients with cemented total hip arthroplasty, 2had ipsilateral total knee arthroplasty. Ten fractureswere in the right femur and 8 in the left. One patient

sustained a fracture after a fall from a horse; the restof the fractures occurred after more conventionalfalls. The average period between original operationand periprosthetic fracture was 8.9 years, with arange of 5 months to 18 years. The fracture patternwas spiral in 13, transverse in 3, and oblique in 2.Nine-hole plate was used in 6 patients, 13-holeplate in 11 patients, and 5-hole plate in 1 patient.The plates were fixed using unicortical screws atthe level of the stem of the prosthesis as well as inthe metaphyseal region, and bicortical screws wereused in diaphyseal region in osteoporotic bonewhere possible. In 5 patients, the plate was used ina reverse direction (antegrade); some of theserequired contouring to maximize proximal holdon the greater trochanter. Thirteen fractures wereoperated upon by consultant and 5 by experiencedsenior specialist registrars. Small incisions weremade over the fracture site to reduce the fracturesanatomically and were maintained by applyingtemporary cerclage wires (in oblique and spiralfractures) until the LISS plate was applied. It wasour preference to leave 2 or more central holesof the plate at the level of fracture, free of screwsto reduce stress risers by “bridging” the fracturesite. All patients were allowed partial weightbearing as able, before discharge under the super-vision of physiotherapist (except wheelchair boundpatients). The fractures were considered united

Fig. 2. A, Type B1 periprosthetic fracture around cemented total hip arthroplasty. B, Eight months postoperative,radiograph showing evidence of fracture union with good alignment.

448 The Journal of Arthroplasty Vol. 23 No. 3 March 2008

when the patient could bear weight without painat the fracture site, and there was radiographicevidence of callus bridging across at least onecortex of the fracture on both the anteroposteriorand lateral views.

Results

Fracture Union

Fracture union was achieved in all 15 patientswith an average union time of 18.6 weeks (12-28 weeks) (Figs. 1A-3B). One patient had a fall17 days postoperatively, which required a furtherLISS plate fixation. This fracture united 24 weeksafter the second operation. All fractures healed insatisfactory alignment in both coronal and sagittalplanes. There was no loss of reduction despite earlypartial weight bearing, and we believe that it mayactually encourage fracture union.

Hospital Stay and Discharge

The average delay between the admission andoperation for these patients was 3 days (range, 0-9).

The average duration of anesthesia was 125 minutes(range, 90-180 minutes). The average hospital staywas 24 days (6-63). There were 4 patients whoremained in the hospital for more than 35 days. Thereason for the delay was lack of beds in arehabilitation unit.

Functional Outcome

Four of the 15 patients were independently mobilebefore the fracture of these 2 patients remainedindependently mobile, and 2 patients used 1 stick atthe time of final follow-up. Four patients used 1 stickbefore the injury of which 1 continued to walk withone stick and 3 required a frame after the surgery.Two patients were using 2 sticks before the injury,and both required a frame after the surgery. Threepatients were using frames before the injury andcontinued to use frames postoperatively. Twopatients used wheelchairs for most of the time beforeinjury and remainedwheelchair bound after surgery.

The average time to full weight bearing was10.7 weeks (6-20 weeks). Two patients whowere wheelchair bound before the injury wereexcluded from the weight-bearing data. The average

Fig. 3. A, Type B1 periprosthetic fracture around uncemented total hip arthroplasty. B, Radiograph showing evidence offracture union with good alignment.

Less Invasive Stabilization System � Kumar et al 449

knee flexion was 101° (85°-130°). One of thewheelchair-bound patients had a preoperativefixed flexion deformity of 50° at the knee, whichremained unchanged.

ComplicationsHardware Problems. Three patients had a mild-

to-moderate discomfort because of the prominentimplants. In 2 of these patients, the plate was used inreverse (antegrade). This allowed better fixation ofproximal fracture fragment because it allowedplacement of multiple screws into the greatertrochanter. Because these plates are not designedto fit around the greater trochanter, in 2 patients,the plates remained prominent under the soft tissueproximally. Designing a proximal femoral LISS platein the future may address this problem. It was notedthat, in one patient, the plate had lifted off the boneat the proximal end with loosening of the screws butwithout loss of reduction of the fracture. Thefracture united at 18 weeks with satisfactoryfunctional outcome. However, no incidence offracture of the plate was noted in our study.

Infection. One patient had a chronic sinus in theposterior aspect of distal thigh with low-gradechronic infection around the prosthesis. Despitethe infection, the fracture united at 28 weeks. Weare not sure whether this was a concealed preexist-ing low-grade infection because of the loose hip

prosthesis (Vancouver's B2) before injury. How-ever, the patient refused further interventionregarding this problem.

Discussion

The aim of the management of periprostheticfractures of the femur is fracture union with earlymobilization and a rapid return to the prefracturestate. There are various methods described for themanagement of this injury. Frigg et al [8] in theiranatomical study of LISS plates found that uni-cortical purchase was sufficient to ensure thestability of the fracture. This is particularly usefulin the management of periprosthetic fractureswhere the femoral stem obstructs the access to theopposite cortex.

Dennis et al [1] in their biomechanical studycomparing various different configurations of fixa-tion of periprosthetic fractures showed that a plate,proximal cables, and distal bicortical screws gave astronger and more rigid fixation than that providedby 2 cortical allograft struts fixed by cables.

There is paucity in the literature on the use of LISSfor periprosthetic fractures of femur around afemoral stem. O'Toole et al [6] reviewed 24 patientstreated with this implant in periprosthetic fracture offemur. Of these, 10 patients were with hip

450 The Journal of Arthroplasty Vol. 23 No. 3 March 2008

arthroplasties and 5 patients had ipsilateral hip andknee arthroplasty. The remaining 9 patients hadtotal knee arthroplasty. Nineteen patients wereavailable for review. Eighteen of the 19 fractureshealed without complications.Haddad et al [9] reviewed 40 patients with the

fractures around a well-fixed femoral stem treatedwith cortical onlay strut allografts with or withoutplates. Ninety-eight percent of the fractures united,and strut-to-host bone unionwas seenwithin the firstyear. There were 4 malunions and 1 deep infection.However, the use of either plates or cortical onlaystruts with bone grafting materials increased theheterogeneity of the treatment methods in this study.In another study by Ricci et al [10], lateral plate

fixation appears to be successful in the managementof periprosthetic fractures. Forty-one patients withtype B1 periprosthetic fractures were treated withuse of indirect reduction techniques and internalfixation with a single lateral plate with screws andcables without bone graft. They noted that allfractures healed with satisfactory alignment. Theynoted that 3 patients had hardware failure andanother 3 patients with infection (1 early + 2 late). Itis clear that they have used different variety of platesand cables/screws, indicating heterogeneity of thetreatment and also implant construct has not beentested biomechanically.In the current study, all patients had homogenous

treatment with LISS plate without the use of bonegraft or combination of cables. Utmost attention wasgiven to the soft tissues and preservation of theblood supply by using this less invasive method. Allfractures healed with satisfactory alignment withminimal complications despite most of the patientsbeing elderly females (average age, 81.6 years) whohad significant comorbidities. Periprosthetic fracturesgenerally occur after low-velocity falls. These frac-tures are more often spiral with minimal comminu-tion, and anatomical reduction with bony stability isachievable. We believe that, by avoiding excessivesoft tissue stripping using the limited invasivestabilization system, potential need for bone graftingcould be avoided. All the patients were allowedearly partial weight bearing, which is a key factor inreducing perioperative morbidity. This was possiblebecause of the increased primary stability of thelocking construct.The satisfactory out come in this preliminary

study appears to be promising for the use of LISS inthe management of Vancouver type B1 and C

periprosthetic fractures for femur. Although notrecommended, this method may be used for fixationof Vancouver type B2 periprosthetic fracture inpatients who are unfit for revision arthroplasty.

However, the limitations of this study include noappropriate hip score because it is a retrospectivestudy and the follow-up was only until completefracture union. Although all the fractures unitedwith satisfactory alignment at the final follow-up,the long-term effects and complications of thisconstruct in the presence of the prosthesis will bedetermined in due course of time.

References

1. Dennis MG, Simon JA, Kumer FJ, et al. Fixation ofperiprosthetic femoral shaft fractures occurring at thetip of the stem. A biomechanical study of 5 techniques.J Arthroplasty 2000;15:523.

2. Learmonth ID. The management of periprostheticfractures around the femoral stem. J Bone Joint SurgBr 2004;86:13.

3. Borrelli J, Prickett W, Song E, et al. Extraosseous blood supply of the tibia and the effects ofdifferent plating techniques: a human cadaver study.J Orthop Trauma 2002;16:691.

4. Marti A, Fankhauser C, Frenk A, et al. Biomechanicalevaluation of the less invasive stabilization system forthe internal fixation of distal femur fractures. J OrthopTrauma 2001;15:482.

5. Bon MR, Egol KA, Koval KJ, et al. Comparison of theLISS and a retrograde-inserted supracondylar intra-medullary nail for fixation of a periprosthetic distalfemur fracture proximal to a total knee arthroplasty.J Arthroplasty 2002;17:876.

6. O'Toole RV, Gobezie R, Hwang R, et al. Lowcomplication rate of LISS for femur fractures adjacentto stable hip or knee arthroplasty. Clin Orthop RelatRes 2006;450:203.

7. Duncan CP, Masri BA. Fractures of the femur after hipreplacement. Instr course Lect 1995;45:293.

8. Frigg R, Appenzeller A, Christensen R, et al. Thedevelopment of the distal femur Less InvasiveStabilisation System (LISS). Injury 2001;32:S-C-24.

9. Haddad FS, Duncan CP, Berry DJ, et al. Peri-prosthetic femoral fractures around well fixedimplants: use of cortical onlay allografts with orwithout a plate. J Bone Joint Surg 2002;84-A:945.

10. Ricci WM, Bolhofner BR, Loftus T, et al. Indirectreduction and plate fixation, without grafting, forperiprosthetic femoral shaft fractures about a stableintramedullary implant. J Bone Joint Surg Am 2005;87:2240.