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Risk factors for periprosthetic femoral fracture
Injury, Int. J. Care Injured (2007) 38, 655—660
www.elsevier.com/locate/injury
Risk factors for periprosthetic femoral fracture John Franklin a,*, Henrik Malchau b a
Massachusetts General Hospital, Boston, MA, United States Department of Orthopaedics, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, GRJ 1126, Boston, MA 02114, United States
b
Accepted 27 February 2007
KEYWORDS Total hip arthroplasty; Periprosthetic fracture; Risk factors; Prevention
Summary Periprosthetic femur fractures are associated with high patient morbidity and are difficult reconstructive challenges. Early identification and appropriate intervention are caritical to prevent this complication. Studies varying from case reports to national arthroplasty registry databases have demonstrated that certain factors are associated with an increased risk of fracture. These include trauma, patient-specific problems, and technical issues related to the hip replacement itself. Recent evidence from large registries has shown that the key to prevention of periprosthetic femur fractures is routine follow-up with radiographic studies. # 2007 Elsevier Ltd. All rights reserved.
Introduction Periprosthetic femoral fracture is a devastating complication after total hip arthroplasty and is associated with a high rate of postoperative complications and often a poor clinical result.20,35 Moreover, the mortality rate after periprosthetic femoral fracture is alarmingly high.4 For these reasons it is important to identify risk factors that lead to fracture. Mont and Maar found most studies in their review of the literature to be small and varied in the type of data reported.28 Another challenge is the relative lack of studies of late fractures after * Corresponding author at: Adult Reconstructive Service, Department of Orthopaedics, Massachusetts General Hospital, Yawkey Building Suite 3700-3B, 55 Fruit Street, Boston, MA 02114, United States. Tel.: +1 617 726 3866; fax: +1 617 726 3883. E-mail address: [email protected] (J. Franklin).
cementless implants.38 More recent clinical studies and published registry data have contributed to our understanding of the aetiology of late periprosthetic fracture, and have led to identification of several risk factors.
Trauma The mechanism of periprosthetic fracture has been frequently investigated.1 Not surprisingly, the majority of the time, low-energy falls are the traumatic event that causes the fracture.23,31 Minor trauma, or falls at the same level at which the patient had been sitting or standing, accounted for approximately 75% of periprosthetic fractures in patients in the Swedish registry database.23 Again highlighting the lack of quality bone stock remaining
0020–1383/$ — see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.injury.2007.02.049
656 after multiple procedures, spontaneous fractures occurred more commonly after revisions (37%) than after primaries (18%). Beals and Tower found the most common mechanism of fracture was a fall at home (66%) or outdoors (18%).1 They reported 8% of all fractures occurring spontaneously. High-energy trauma appears to account for a much smaller percentage of periprosthetic femoral fractures. Not surprisingly, Beals and Tower found high-energy trauma to produce comminuted fractures, whereas low-energy trauma more often produced simple transverse fractures.1
Age Age is frequently cited as a risk factor for late fracture. Related to remaining bone quality, previous surgery, and medical comorbidities, the risk imparted by age is probably multifactorial,21 and evidence supporting age as a risk factor varies widely. Among studies investigating the age of patients sustaining fractures, reported mean ages have been ranged from 60 to 77 years. Age is associated with other problems like osteoporosis and falls which put the patient at greater risk. Wu reviewed 16 fractures out of 454 cementless total hip arthroplasties and found a significant association with an elevated risk of fracture and the patient’s age.38 Patients with a postoperative fracture averaged 65.6 years of age, whereas those in the non-fracture group averaged 52.6 years of age. In their review of the Swedish registry, Lindahl et al. also found a higher risk of periprosthetic fracture for both age and every year of aging after the primary procedure.21 In this study, the risk ratio for fracture was 1.01 per additional year of aging. In addition to the age of the patient, the time from the index operation is likely to be an important factor in risk assessment. In contrast, Sarvilinna et al. did not find an association between advanced age and fracture risk.30 In their review of 16 periprosthetic fractures from the Finnish registry, age less than 70 years at the time of the index operation was a significant risk factor. These patients, all of whom had undergone arthroplasty after hip fracture, had an odds ratio of 4.9 compared with a group of control patients with similar diagnoses and treatment. Lindahl found that younger age at the time of the index operation in their series increased the risk for subsequent fracture compared with the remaining population of patients undergoing total hip replacement.22 This finding suggests that higher activity levels in younger patients over a sustained period of time puts these patients at higher risk of fracture.
J. Franklin, H. Malchau
Gender A higher proportion of periprosthetic fractures among female patients has been reported.1,3,15,37 Reported percentages of fractures in females in these studies have ranged from 52% to 70%. As a result of these numbers, Tsiridis claimed that gender was a risk factor for postoperative fracture.36 The significance of gender is probably multifactorial, as it also is associated with osteoporosis and remaining structural bone. Swedish joint registry data show an almost equal gender distribution in younger age groups, whereas among patients older than 80 years, fractures are more prevalent among females. Others have found essentially no significant difference in fracture rate in relation to gender.22 The Swedish registry reported a statistically insignificant higher proportion of female patients sustaining fractures after both primary and revision total hip arthroplasty. However, the overall percentage of hip arthroplasties in Sweden is higher in the female population (60%). As a result, females actually had a lower risk of fracture than males.21 Finnish registry data support the finding that there is no higher risk according to gender. Among the 31 periprosthetic fractures treated between 1990 and 1999 with revision, there was no greater risk for fracture in the female cohort.31
Osteoporosis Osteoporosis is a generally accepted risk factor for late periprosthetic femoral fracture.10,17,19,21 However, few studies have systematically investigated the effect of the patient’s bone quality on subsequent fracture risk. Wu 1999 looked at 16 postoperative fractures in a series of 454 consecutive arthroplasties.38 Using Singh’s index of osteoporosis, preoperative osteoporosis was found to be a significant predictor of fracture risk. Beals and Tower found that 38% of patients in their series had sustained a previous vertebral or metaphyseal fracture, and many others had evidence of osteopenia.1 In addition, the high percentage of fractures caused by low-energy falls points to bone fragility as a predispoding factor.21
Index diagnosis Different diagnoses often lead to specific patient care decisions. Similarly, the patient diagnosis prior to hip arthroplasty has been demonstrated to impart some degree of risk for periprosthetic fracture.
Periprosthetic femoral fracture Rheumatoid arthritis is often associated with diffuse osteopenia and other medical comorbidities. In the Swedish registry, rheumatoid arthritis was overrepresented in the group of patients sustaining periprosthetic fracture.23 In addition, when evaluated as a risk factor, rheumatoid arthritis was associated with an elevated hazard ratio of 1.56.21 Data from the Finnish registry confirm this finding, demonstrating a risk ratio of 2.1.31 Perhaps related to associated age and poor bone quality, periprosthetic fractures have also been found to occur more commonly in patients with a hip fracture prior to arthroplasty. Registry data again support this conclusion. In Finland, the diagnosis of hip fracture had twice the risk for postoperative periprosthetic fracture compared with rheumatoid arthritis (risk ratio 4.4 versus 2.1).31 In Sweden, similar results were observed, as hip fracture was associated with the highest risk of periprosthetic fracture among demographic variables.21
Osteolysis Osteolysis by itself is frequently cited as a risk factor for late periprosthetic femoral fracture.29,32,36 Described by Harris, localised femoral bone loss in association with a loose cemented stem was thought to be mediated by the failed cement.11 Now recognised to be the end result of a response to wear particles, osteolysis is still an enormous problem in both cemented as well as cementless hip arthroplasty.24,25 The most common cause of late periprosthetic fracture is osteolysis and the resultant aseptic loosening.19 Schmidt proposed that an osteolytic lesion near the tip of a femoral stem was the equivalent of an impending pathological fracture of a subtrochanteric metastasis.32 Pazzaglia reported one of the earliest cases of periprosthetic fracture through an osteolytic lesion.29 Brown and Ring followed this with their series of 10 patients with extensive osteolysis throughout the proximal femur.5 Patients in this study frequently had resportion or fracture through the lesions in the trochanters. Indeed, osteolysis of the greater trochanter is a problem that has persisted, and it is still associated with fracture and decreased implant survival.12 Late periprosthetic fracture associated with osteolysis has been recognised as a growing problem in arthroplasty.2 Surgical approaches to this problem must not only address the deficient remaining bone and possibly a loose implant, but also the issue of the wear particle generator.2,17
657
Aseptic loosening Aseptic loosening is typically mediated by osteolysis, but the two terms are often used interchangeably. Loosening of femoral stems as a result of osteolysis is characterised by localised or diffuse endosteal bone resorption. Loose implants have been demonstrated to be risk factors for periprosthetic fracture in several studies.13,36 Bethea et al. suggested that loosening of the stem led to increased motion at the cement— bone interface, resulting in further bone resorption.3 In their series of 31 cases, 75% demonstrated pre-fracture evidence of loosening. Both Jensen and Fredin reported that approximately half of the patients in their series demonstrated evidence of loosening at the time of fracture.6,14 Tower and Beals noted 22/93 cases had a loose femoral stem prior to fracture.35 More recent data have emphasised the importance of stem stability in fracture risk. Lindahl et al. investigated risk factors in 1049 cases from the Swedish registry between 1979 and 2000.23 In patients sustaining fractures after primary hip arthroplasty, 70% of the femoral implants in this series were loose.
Revision Revision total hip arthroplasty is frequently associated with bone loss and challenging implant fixation. Wear debris and resultant osteolysis can reduce available bone stock for fixation at the time of revision. In addition, cortical perforation may occur during cement or implant removal, thus compromising remaining bone integrity. For these reasons, when investigated independently, revision has been identified as a risk factor for periprosthetic fracture.21 Several studies have confirmed the assertion that revision carries inherent fracture risk. The incidence of postoperative fracture has been estimated by Kavanagh to be less than 1% after primary hip arthroplasty and 4% after revision procedures.16 Lewallen and Berry found similar results from their review of the Mayo Clinic Total Joint Registry when they reported a fracture rate of 0.4—0.6% after primary arthroplasties and 1.5—2.8% after revisions.20 The rate of fracture also appears to be directly related to the number of revisions undertaken.21 From the Swedish registry, the strongest risk correlation in the population of revised prostheses was found with an increasing number of previous stem revisions.21 Moreover, the average time interval to
658 fracture diminished with each additional revision procedure.23 The time between surgery and fracture averaged 7.4 years after a primary arthroplasty, 3.9 years after one revision, 3.8 years after two revisions, and 2.3 years after three revisions.23
Implants Different implants have also been shown to impart different levels of late periprosthetic fracture risk depending on specific design characteristics. These differences have been found mainly among cemented stems, as countries where cement is the predominant means of fixation also have the largest series of periprosthetic fractures. From the Finnish registry, Sarvilinna et al. found the Exeter stem to be associated with an increased risk of late fracture compared with all other stems.30 Data from the Swedish registry show an overrepresentation of the Exeter and Charnley stems in the fracture group and an underrepresentation of the Lubinus stem.21 These are the three most commonly used cemented stems in Sweden and each has unique design features. The Lubinus stem is anatomically shaped, has a small collar and a matte finish. It is also longer than either of the other two stems. The Exeter stem is a polished, straight, double-taper design. The Charnley is straight with a large proximal flange and matte finish. The Charnley and Exeter stems are both short and straight, and both have the inherent limitations of appropriate positioning and of affording an adequate cement mantle with this design.8,9 Additionally, a taper design can increase hoop stresses in the cement and proximal femur, thereby predisposing the patient to periprosthetic fracture. The Lubinus is not limited by these features. With its anatomical design, an adequate cement mantle can be achieved. Little is known about how the design features of cementless implants affect a patient’s risk for subsequent periprosthetic fracture. Beals and Tower, however, found fractures with cementless implants to be associated with technique-dependent stress risers.1
Technique Any surgical factor that decreases bone strength is a risk factor for late fracture. These include screw holes and stress risers from adjacent implants.7,32 Cortical perforations may result from osteolytic lesions, previous hardware or during
J. Franklin, H. Malchau cement or implant removal. McElfresh and Coventry described reaming of the femoral canal, osteoporosis, a narrow medullary canal and previous prosthesis or osteotomy as factors increasing the chances of creating a cortical perforation.27 These defects can have a significant effect on the strength properties of the remaining femoral bone stock.32 Larson found that fenestrations created in the anterolateral cortex of sheep femora produced a reduction in torsional strength of 44%. Bypassing the defect by two diaphyseal diameters with a cemented stem improved this value to 84% of the intact control side. Clinical studies have demonstrated a relationship between a localised area of compromised bone and a late periprosthetic fracture.6,34 Bethea et al. found that the fractures associated with minor trauma often occurred near a previous cortical breach.3 In Scott’s series, four of five postoperative fractures occurred at the tip of the stem through a cortical defect.33 Tower and Beals found that many of their fractures, particularly those previously revised, were located along cortical stress risers.35 Johansson’s series demonstrates the effect on fracture risk of different stress risers in hip arthroplasty.15 Of 14 patients who developed periprosthetic fractures, three occurred through a cortical window, two occurred through old screw holes and one patient often experienced fracture between the femoral stem and existing distal plates.
Prevention Prevention of late periprosthetic femoral fracture is best accomplished through routine clinical and radiographic follow-up.21 Regular monitoring of patients allows for early detection of osteolysis and aseptic loosening, and thus facilitates timely revision surgery.32 Several technical factors can help prevent late fracture. Great care must be taken when reaming the canal or removing cement in patients with known risk factors for fracture, such as rheumatoid arthritis, or those patients who have undergone previous hip surgery.10 Cortical defects and osteolytic lesions near the tip of the stem should be grafted and bypassed with long femoral stems when recognised during surgery.7,32 Cortical strut grafts can be used prophylactically to reinforce cortical defects and other stress risers.7 The treatment of osteolytic lesions of the trochanters is controversial, and should be based on patient symptoms and individual functional demands.
Periprosthetic femoral fracture
659
Conclusions Given the variable results of treatment for late periprosthetic femoral fracture, every means necessary to prevent this complication must be undertaken. The surgeon must keep in mind patient factors that increase the chance of fracture, including age, gender and index diagnosis. Compromised bone stock in both complex primary and revision surgery must be addressed. Finally, routine follow-up of patients after total hip arthroplasty is critical in identifying those at high risk of fracture.
13.
14.
15.
16. 17. 19.
Conflict of interest statement
20.
Dr. Franklin has no financial relationship with any member of the orthopaedic industry. Dr. Malchau has a financial relationship with Zimmer, Biomet, and Smith and Nephew.
21.
22.
References 23. 1. Beals RK, Tower SS. Periprosthetic fractures of the femur. An analysis of 93 fractures. Clin Orthop 1996;327: 238—46. 2. Berry DJ. Periprosthetic fractures associated with osteolyis: a problem on the rise. J Arthroplasty 2003;18:107—11. 3. Bethea JS, DeAndrade R, Fleming LL. Proximal femoral fractures following total hip arthroplasty. Clin Orthop 1982;170: 95—106. 4. Bhattacharyya T. Mortality after periprosthetic fracture of the femur (unpublished data). 5. Brown IW, Ring PA. Osteolytic changes in the upper femoral shaft following porous-coated hip replacement. J Bone Joint Surg Br 1985;67:218—21. 6. Fredin HO, Lindberg H, Carlsson AS. Femoral fracture following hip arthroplasty. Acta Orthop Scand 1987;58: 20—2. 7. Garbuz DS, Masri BA, Duncan CP. Periprosthetic fractures of the femur: principles of prevention and management. Instr Course Lect 1998;47:237—42. 8. Garellick G, Malchau H, Herberts P. The Charnley versus the Spectron hip prosthesis: clinical evaluation of a randomized, prospective study of 2 different hip implants. J Arthroplasty 1999;14:407—13. 9. Garellick G, Malchau H, Regner H, Herberts P. The Charnley versus the Spectron hip prosthesis: radiographic evaluation of a randomized, prospective study of 2 different hip implants. J Arthroplasty 1999;14:414—25. 10. Haddad FS, Masri BA, Garbuz DS, Duncan CP. The prevention of periprosthetic fractures in total hip and knee arthroplasty. Orthop Clin North Am 1999;30:191—207. 11. Harris MB, Schiller AL, Scholler JM. Extensive localized bone resorption in the femur following total hip replacement. J Bone Joint Surg Am 1976;58:612—8. 12. Hsieh PH, Chang YH, Lee PC, Shih CH. Periprosthetic fractures of the greater trochanter through osteolytic cysts with uncemented MicroStructured Omnifit prosthesis: retrospec-
24.
25.
27.
28.
29.
30.
31.
32. 33.
34.
tive analyses of 23 fractures in 887 hips after 5—14 years. Acta Orthop 2005;76:538—43. Incavo SJ, Beard DM, Pupparo F, et al. One-stage revision of periprosthetic fractures around loose cemented total hip arthroplasty. Am J Orthop 1998;27:35—41. Jensen JS, Barfod G, Hansen D, et al. Femoral shaft fracture after hip arthroplasty. Acta Orthop Scand 1988;59:9—13. Johansson JE, McBroom R, Barrington TW, Hunter GA. Fracture of the ipsilateral femur in patients with total hip replacement. J Bone Joint Surg Am 1981;63:1435—42. Kavanagh BF. Femoral fractures associated with total hip arthroplasty. Orthop Clin North Am 1992;23:249—57. Kelley SS. Periprosthetic femoral fractures. J Am Acad Orthop Surg 1994;2:164—72. Learmonth ID. The management of periprosthetic fractures around the femoral stem. J Bone Joint Surg Br 2004;8: 613—9. Lewallen DG, Berry DJ. Periprosthetic fracture of the femur after total hip arthroplasty: treatment and results to date. Instr Course Lect 1998;47:243—9. Lindahl H, Eisler T, Oden A, et al. Risk factors associated with the late periprosthetic femoral fracture. In: Lindahl H, editor. The periprosthetic femur fracture: a study from the Swedish National Hip Arthroplasty Register. Goteberg: Department of Orthopaedics, Sahlgenska Academy, Goteberg University; 2006. Lindahl H, Garellick G, Regner H, et al. Three hundred and twenty-one periprosthetic femoral fractures. J Bone Joint Surg Am 2006;88:1215—22. Lindahl H, Malchau H, Herberts P, Garellick G. Periprosthetic femoral fractures: classification and demographics of 1049 periprosthetic femoral fractures from the Swedish National Hip Arthroplasty Register. J Arthroplasty 2005;20: 857—65. Malchau H, Herberts P, Ahnfelt L. Prognosis of total hip replacement in Sweden. Follow-up of 92,675 operations performed 1978—1990. Acta Orthop Scand 1993;64: 497—506. Maloney WJ, Jasty M, Harris WH, et al. Endosteal erosion in association with stable uncemented femoral components. J Bone Joint Surg Am 1990;72:1025—34. McElfresh EC, Coventry MB. Femoral and pelvic fractures after total hip arthroplasty. J Bone Joint Surg Am 1974;56: 483—92. Mont MA, Maar DC. Fractures of the ipsilateral femur after hip arthroplasty. A statistical analysis of outcome based on 487 patients. J Arthroplasty 1994;9:511—9. Pazzaglia U, Byers PD. Fractured femoral shaft through an osteolytic lesion resulting from the reaction to a prosthesis: a case report. J Bone Joint Surg Br 1984;66:337—9. Sarvilinna R, Huhtala H, Pajamaki J. Young age and wedge stem design are risk factors for periprosthetic fracture after arthroplasty due to hip fracture. A case—control study. Acta Orthop 2005;76:56—60. Sarvilinna R, Huhtala HS, Sovelius RT, et al. Factors predisposing to periprosthetic fracture after hip arthroplasty: a case—control study. Acta Orthop Scand 2004;75: 16—20. Schmidt AH, Kyle RF. Periprosthetic fractures of the femur. Orthop Clin North Am 2002;33:143—52. Scott RD, Turner RH, Leitzes SM, Aufranc OE. Femoral fractures in conjunction with total hip replacement. J Bone Joint Surg Am 1975;57:494—501. Talab YA, States JD, Evarts CM. Femoral shaft perforation: a complication of total hip arthroplasty. Clin Orthop 1979;141: 158—65.
660 35. Tower SS, Beals RK. Fractures of the femur after hip replacement: the Oregon experience. Orthop Clin North Am 1999;30:235—47. 36. Tsiridis E, Haddad FS, Gie GA. The management of periprosthetic femoral fractures around hip replacements. Injury 2003;34:95—105.
J. Franklin, H. Malchau 37. Whittaker RP, Lazaros NS, Ralston EL. Fractures of the femur about femoral endoprostheses. J Trauma 1974;14: 675—94. 38. Wu CC, Au MK, Wu SS, Lin LC. Risk factors for postoperative femoral fracture in cementless hip arthroplasty. J Formos Med Assoc 1999;98:190—4.
www.elsevier.com/locate/injury
Risk factors for periprosthetic femoral fracture John Franklin a,*, Henrik Malchau b a
Massachusetts General Hospital, Boston, MA, United States Department of Orthopaedics, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, GRJ 1126, Boston, MA 02114, United States
b
Accepted 27 February 2007
KEYWORDS Total hip arthroplasty; Periprosthetic fracture; Risk factors; Prevention
Summary Periprosthetic femur fractures are associated with high patient morbidity and are difficult reconstructive challenges. Early identification and appropriate intervention are caritical to prevent this complication. Studies varying from case reports to national arthroplasty registry databases have demonstrated that certain factors are associated with an increased risk of fracture. These include trauma, patient-specific problems, and technical issues related to the hip replacement itself. Recent evidence from large registries has shown that the key to prevention of periprosthetic femur fractures is routine follow-up with radiographic studies. # 2007 Elsevier Ltd. All rights reserved.
Introduction Periprosthetic femoral fracture is a devastating complication after total hip arthroplasty and is associated with a high rate of postoperative complications and often a poor clinical result.20,35 Moreover, the mortality rate after periprosthetic femoral fracture is alarmingly high.4 For these reasons it is important to identify risk factors that lead to fracture. Mont and Maar found most studies in their review of the literature to be small and varied in the type of data reported.28 Another challenge is the relative lack of studies of late fractures after * Corresponding author at: Adult Reconstructive Service, Department of Orthopaedics, Massachusetts General Hospital, Yawkey Building Suite 3700-3B, 55 Fruit Street, Boston, MA 02114, United States. Tel.: +1 617 726 3866; fax: +1 617 726 3883. E-mail address: [email protected] (J. Franklin).
cementless implants.38 More recent clinical studies and published registry data have contributed to our understanding of the aetiology of late periprosthetic fracture, and have led to identification of several risk factors.
Trauma The mechanism of periprosthetic fracture has been frequently investigated.1 Not surprisingly, the majority of the time, low-energy falls are the traumatic event that causes the fracture.23,31 Minor trauma, or falls at the same level at which the patient had been sitting or standing, accounted for approximately 75% of periprosthetic fractures in patients in the Swedish registry database.23 Again highlighting the lack of quality bone stock remaining
0020–1383/$ — see front matter # 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.injury.2007.02.049
656 after multiple procedures, spontaneous fractures occurred more commonly after revisions (37%) than after primaries (18%). Beals and Tower found the most common mechanism of fracture was a fall at home (66%) or outdoors (18%).1 They reported 8% of all fractures occurring spontaneously. High-energy trauma appears to account for a much smaller percentage of periprosthetic femoral fractures. Not surprisingly, Beals and Tower found high-energy trauma to produce comminuted fractures, whereas low-energy trauma more often produced simple transverse fractures.1
Age Age is frequently cited as a risk factor for late fracture. Related to remaining bone quality, previous surgery, and medical comorbidities, the risk imparted by age is probably multifactorial,21 and evidence supporting age as a risk factor varies widely. Among studies investigating the age of patients sustaining fractures, reported mean ages have been ranged from 60 to 77 years. Age is associated with other problems like osteoporosis and falls which put the patient at greater risk. Wu reviewed 16 fractures out of 454 cementless total hip arthroplasties and found a significant association with an elevated risk of fracture and the patient’s age.38 Patients with a postoperative fracture averaged 65.6 years of age, whereas those in the non-fracture group averaged 52.6 years of age. In their review of the Swedish registry, Lindahl et al. also found a higher risk of periprosthetic fracture for both age and every year of aging after the primary procedure.21 In this study, the risk ratio for fracture was 1.01 per additional year of aging. In addition to the age of the patient, the time from the index operation is likely to be an important factor in risk assessment. In contrast, Sarvilinna et al. did not find an association between advanced age and fracture risk.30 In their review of 16 periprosthetic fractures from the Finnish registry, age less than 70 years at the time of the index operation was a significant risk factor. These patients, all of whom had undergone arthroplasty after hip fracture, had an odds ratio of 4.9 compared with a group of control patients with similar diagnoses and treatment. Lindahl found that younger age at the time of the index operation in their series increased the risk for subsequent fracture compared with the remaining population of patients undergoing total hip replacement.22 This finding suggests that higher activity levels in younger patients over a sustained period of time puts these patients at higher risk of fracture.
J. Franklin, H. Malchau
Gender A higher proportion of periprosthetic fractures among female patients has been reported.1,3,15,37 Reported percentages of fractures in females in these studies have ranged from 52% to 70%. As a result of these numbers, Tsiridis claimed that gender was a risk factor for postoperative fracture.36 The significance of gender is probably multifactorial, as it also is associated with osteoporosis and remaining structural bone. Swedish joint registry data show an almost equal gender distribution in younger age groups, whereas among patients older than 80 years, fractures are more prevalent among females. Others have found essentially no significant difference in fracture rate in relation to gender.22 The Swedish registry reported a statistically insignificant higher proportion of female patients sustaining fractures after both primary and revision total hip arthroplasty. However, the overall percentage of hip arthroplasties in Sweden is higher in the female population (60%). As a result, females actually had a lower risk of fracture than males.21 Finnish registry data support the finding that there is no higher risk according to gender. Among the 31 periprosthetic fractures treated between 1990 and 1999 with revision, there was no greater risk for fracture in the female cohort.31
Osteoporosis Osteoporosis is a generally accepted risk factor for late periprosthetic femoral fracture.10,17,19,21 However, few studies have systematically investigated the effect of the patient’s bone quality on subsequent fracture risk. Wu 1999 looked at 16 postoperative fractures in a series of 454 consecutive arthroplasties.38 Using Singh’s index of osteoporosis, preoperative osteoporosis was found to be a significant predictor of fracture risk. Beals and Tower found that 38% of patients in their series had sustained a previous vertebral or metaphyseal fracture, and many others had evidence of osteopenia.1 In addition, the high percentage of fractures caused by low-energy falls points to bone fragility as a predispoding factor.21
Index diagnosis Different diagnoses often lead to specific patient care decisions. Similarly, the patient diagnosis prior to hip arthroplasty has been demonstrated to impart some degree of risk for periprosthetic fracture.
Periprosthetic femoral fracture Rheumatoid arthritis is often associated with diffuse osteopenia and other medical comorbidities. In the Swedish registry, rheumatoid arthritis was overrepresented in the group of patients sustaining periprosthetic fracture.23 In addition, when evaluated as a risk factor, rheumatoid arthritis was associated with an elevated hazard ratio of 1.56.21 Data from the Finnish registry confirm this finding, demonstrating a risk ratio of 2.1.31 Perhaps related to associated age and poor bone quality, periprosthetic fractures have also been found to occur more commonly in patients with a hip fracture prior to arthroplasty. Registry data again support this conclusion. In Finland, the diagnosis of hip fracture had twice the risk for postoperative periprosthetic fracture compared with rheumatoid arthritis (risk ratio 4.4 versus 2.1).31 In Sweden, similar results were observed, as hip fracture was associated with the highest risk of periprosthetic fracture among demographic variables.21
Osteolysis Osteolysis by itself is frequently cited as a risk factor for late periprosthetic femoral fracture.29,32,36 Described by Harris, localised femoral bone loss in association with a loose cemented stem was thought to be mediated by the failed cement.11 Now recognised to be the end result of a response to wear particles, osteolysis is still an enormous problem in both cemented as well as cementless hip arthroplasty.24,25 The most common cause of late periprosthetic fracture is osteolysis and the resultant aseptic loosening.19 Schmidt proposed that an osteolytic lesion near the tip of a femoral stem was the equivalent of an impending pathological fracture of a subtrochanteric metastasis.32 Pazzaglia reported one of the earliest cases of periprosthetic fracture through an osteolytic lesion.29 Brown and Ring followed this with their series of 10 patients with extensive osteolysis throughout the proximal femur.5 Patients in this study frequently had resportion or fracture through the lesions in the trochanters. Indeed, osteolysis of the greater trochanter is a problem that has persisted, and it is still associated with fracture and decreased implant survival.12 Late periprosthetic fracture associated with osteolysis has been recognised as a growing problem in arthroplasty.2 Surgical approaches to this problem must not only address the deficient remaining bone and possibly a loose implant, but also the issue of the wear particle generator.2,17
657
Aseptic loosening Aseptic loosening is typically mediated by osteolysis, but the two terms are often used interchangeably. Loosening of femoral stems as a result of osteolysis is characterised by localised or diffuse endosteal bone resorption. Loose implants have been demonstrated to be risk factors for periprosthetic fracture in several studies.13,36 Bethea et al. suggested that loosening of the stem led to increased motion at the cement— bone interface, resulting in further bone resorption.3 In their series of 31 cases, 75% demonstrated pre-fracture evidence of loosening. Both Jensen and Fredin reported that approximately half of the patients in their series demonstrated evidence of loosening at the time of fracture.6,14 Tower and Beals noted 22/93 cases had a loose femoral stem prior to fracture.35 More recent data have emphasised the importance of stem stability in fracture risk. Lindahl et al. investigated risk factors in 1049 cases from the Swedish registry between 1979 and 2000.23 In patients sustaining fractures after primary hip arthroplasty, 70% of the femoral implants in this series were loose.
Revision Revision total hip arthroplasty is frequently associated with bone loss and challenging implant fixation. Wear debris and resultant osteolysis can reduce available bone stock for fixation at the time of revision. In addition, cortical perforation may occur during cement or implant removal, thus compromising remaining bone integrity. For these reasons, when investigated independently, revision has been identified as a risk factor for periprosthetic fracture.21 Several studies have confirmed the assertion that revision carries inherent fracture risk. The incidence of postoperative fracture has been estimated by Kavanagh to be less than 1% after primary hip arthroplasty and 4% after revision procedures.16 Lewallen and Berry found similar results from their review of the Mayo Clinic Total Joint Registry when they reported a fracture rate of 0.4—0.6% after primary arthroplasties and 1.5—2.8% after revisions.20 The rate of fracture also appears to be directly related to the number of revisions undertaken.21 From the Swedish registry, the strongest risk correlation in the population of revised prostheses was found with an increasing number of previous stem revisions.21 Moreover, the average time interval to
658 fracture diminished with each additional revision procedure.23 The time between surgery and fracture averaged 7.4 years after a primary arthroplasty, 3.9 years after one revision, 3.8 years after two revisions, and 2.3 years after three revisions.23
Implants Different implants have also been shown to impart different levels of late periprosthetic fracture risk depending on specific design characteristics. These differences have been found mainly among cemented stems, as countries where cement is the predominant means of fixation also have the largest series of periprosthetic fractures. From the Finnish registry, Sarvilinna et al. found the Exeter stem to be associated with an increased risk of late fracture compared with all other stems.30 Data from the Swedish registry show an overrepresentation of the Exeter and Charnley stems in the fracture group and an underrepresentation of the Lubinus stem.21 These are the three most commonly used cemented stems in Sweden and each has unique design features. The Lubinus stem is anatomically shaped, has a small collar and a matte finish. It is also longer than either of the other two stems. The Exeter stem is a polished, straight, double-taper design. The Charnley is straight with a large proximal flange and matte finish. The Charnley and Exeter stems are both short and straight, and both have the inherent limitations of appropriate positioning and of affording an adequate cement mantle with this design.8,9 Additionally, a taper design can increase hoop stresses in the cement and proximal femur, thereby predisposing the patient to periprosthetic fracture. The Lubinus is not limited by these features. With its anatomical design, an adequate cement mantle can be achieved. Little is known about how the design features of cementless implants affect a patient’s risk for subsequent periprosthetic fracture. Beals and Tower, however, found fractures with cementless implants to be associated with technique-dependent stress risers.1
Technique Any surgical factor that decreases bone strength is a risk factor for late fracture. These include screw holes and stress risers from adjacent implants.7,32 Cortical perforations may result from osteolytic lesions, previous hardware or during
J. Franklin, H. Malchau cement or implant removal. McElfresh and Coventry described reaming of the femoral canal, osteoporosis, a narrow medullary canal and previous prosthesis or osteotomy as factors increasing the chances of creating a cortical perforation.27 These defects can have a significant effect on the strength properties of the remaining femoral bone stock.32 Larson found that fenestrations created in the anterolateral cortex of sheep femora produced a reduction in torsional strength of 44%. Bypassing the defect by two diaphyseal diameters with a cemented stem improved this value to 84% of the intact control side. Clinical studies have demonstrated a relationship between a localised area of compromised bone and a late periprosthetic fracture.6,34 Bethea et al. found that the fractures associated with minor trauma often occurred near a previous cortical breach.3 In Scott’s series, four of five postoperative fractures occurred at the tip of the stem through a cortical defect.33 Tower and Beals found that many of their fractures, particularly those previously revised, were located along cortical stress risers.35 Johansson’s series demonstrates the effect on fracture risk of different stress risers in hip arthroplasty.15 Of 14 patients who developed periprosthetic fractures, three occurred through a cortical window, two occurred through old screw holes and one patient often experienced fracture between the femoral stem and existing distal plates.
Prevention Prevention of late periprosthetic femoral fracture is best accomplished through routine clinical and radiographic follow-up.21 Regular monitoring of patients allows for early detection of osteolysis and aseptic loosening, and thus facilitates timely revision surgery.32 Several technical factors can help prevent late fracture. Great care must be taken when reaming the canal or removing cement in patients with known risk factors for fracture, such as rheumatoid arthritis, or those patients who have undergone previous hip surgery.10 Cortical defects and osteolytic lesions near the tip of the stem should be grafted and bypassed with long femoral stems when recognised during surgery.7,32 Cortical strut grafts can be used prophylactically to reinforce cortical defects and other stress risers.7 The treatment of osteolytic lesions of the trochanters is controversial, and should be based on patient symptoms and individual functional demands.
Periprosthetic femoral fracture
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Conclusions Given the variable results of treatment for late periprosthetic femoral fracture, every means necessary to prevent this complication must be undertaken. The surgeon must keep in mind patient factors that increase the chance of fracture, including age, gender and index diagnosis. Compromised bone stock in both complex primary and revision surgery must be addressed. Finally, routine follow-up of patients after total hip arthroplasty is critical in identifying those at high risk of fracture.
13.
14.
15.
16. 17. 19.
Conflict of interest statement
20.
Dr. Franklin has no financial relationship with any member of the orthopaedic industry. Dr. Malchau has a financial relationship with Zimmer, Biomet, and Smith and Nephew.
21.
22.
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