Aging Clinical and Experimental Research
Periprosthetic femoral fractures: risk factors and current options to treatment Antonio Capone, Franco Ennas and Daniele Podda Orthopaedic Department, University of Cagliari, Cagliari, Italy ABSTRACT. The incidence and complexity of the femoral fracture around a previously implanted prosthetic component has been increasing over the last ten years, and treatment can be complex, expensive and associated with an increased risk of local and systemic complications. The surgical treatment options for periprosthetic fractures include open reduction and internal fixation of bone or revision arthroplasty. This review focuses on the current surgical techniques and the pharmacological therapy to provide biological support for the enhancement of bone healing. (Aging Clin Exp Res 2011; 23 (Suppl. to No. 2): ##-##) ©2011,
Editrice Kurtis
EPIDEMIOLOGY AND RISK FACTORS The incidence of periprosthetic femoral fractures seems to be increasing because of a number of factors: the increasing prevalence of patients with femoral prostheses; the increasing number of elderly patients at risk for osteoporosis; the increasing numbers of young patients with THA at risk for high-energy trauma events; and the increasing numbers of revision procedures. Lindhal et al. (1) reported an annual incidence of 0.11% in 2000 compared to 0.045% in 1998 for all total hip arthroplasties performed in Sweden, with 0.4% of accumulated incidence for the primary total hip arthroplasty and 2.1% for the revision implants. The Annual report of Swedish hip arthroplasty register (ed. 2008) stated the occurence of reoperation for fractures were 10.25% in the period 1979-2008 (2). Consequently, periprosthetic femoral fractures usually result from low-energy trauma and frequently occur after falls or even spontaneously during normal daily living activity. Lindahl et al. (1) reported only 7% of periprosthetic femoral fractures were the result of major trauma, whereas 75% occurred from a fall from either the seated or standing position, and 18% occurred spontaneously. Osteolysis by itself is frequently cited as a risk factor for late periprosthetic femoral fracture. Localised femoral bone loss is now recognised to be the end result of a response to wear particles in both cemented
and cementless hip arthroplasty. The stem stability has been demonstrated to be an important risk factor for fracture. Lindhal et al. (1) found that in the patients sustaining femoral periprosthetic fractures after primary hip arthroplasty, 70% of the femoral stems were loose. SURGICAL TREATMENT Periprosthetic femoral fractures represent a challenge for orthopaedic surgeon requiring the skills of revision surgery as well as those of trauma surgery. This physiologic shock to such a frail patient is considerable, but can be reduced by anticipating potential problems such as large blood loss, healing potential, and prolonged rehabilitation. The current gold standard for the treatment of post-traumatic periprosthetic femoral fractures is surgery, with an exception to selected simple fractures being given a stable implant, which can be treated conservatively with bed rest or braces. Consequently, it is imperative to correctly identify the type of fracture and the stability of the implant for correct surgical planning. The Vancouver classification of periprosthetic fractures of the hip is considered a reliable grading system that provides a guide for treatment choices (3). In particular, the Vancouver classification differentiate stable from unstable implants which require revision surgery. Fractures involving the trochanteric are categorized as type A (AG and AL for the greater and lesser trochanter, respectively). Type B fractures are further divided into subtype B1 when adjacent to a well fixed stem, B2 in the presence of a loose stem, and B3 when associated with marked osteopenia or bone loss. Type C are fractures involving the femur well below the femoral stem. The choice of treatment is based upon the type of fracture, the integrity and quality of the bone stock, and the stability of the original implant according to an algorithm proposed by Masri et al. (3). Type B1 fractures (well fixed stem) can be treated successfully with open reduction and internal fixation (ORIF). For this purpose, several cable plate systems are available including the Ogden plate, Dall-Miles plate
Key words: Osteoporosis, periprosthetic fractures, total hip arthroplasty. Correspondence: Prof. Antonio Capone, Clinica Ortopedica, Ospedale Marino, Lungomare Poetto, 09126, Cagliari, Italy. E-mail:
[email protected]
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A. Capone, F. Ennas and D. Podda
(Stryker, New Jersey, US), cable-ready plate (Zimmer, Warsaw, Indiana) and Peri-fix plate (Merete, Berlin, Germany). These systems allow attachment of cables, wires, and screws, providing the surgeon with many options for securing the plate to the fractured femur without interfering with the intramedullary device or the cement mantle. More recent designs allow cables and screws to be alternated along the plate (as the fracture requires) and the screws to lock into the plate providing angular stability to achieve optimal fracture fixation. The locking compression plate allows a biological fixation layout and a less invasive surgery approach. Wood et al. (4) reported the two-year follow-up results in 16 Vancouver type B1 and C fractures fixed with the LCP system. There were 6 patients who had had a failure of their previous periprosthetic fracture fixation and who required revision surgery. They advocated a minimum of 10 cortices of fixation above and below the fracture. In Type B2 fractures the femoral component is loose and therefore these are treated with an implant revision. By using non-cemented modular stems, it is possible to bypass the fracture site and achieve distal cortical fixation. Springer et al. (5) demonstrated a prosthetic survival of 90% at 5 years and 79.2% at 10 years for 118 hips treated by long-stem revision arthroplasty for type B periprosthetic femoral fracture. In type B3 fractures, due to the great amount of bone loss, it is advisable to augment the revision surgery with cancellous bone impaction grafting or strut-grafting with cerclage wires. The loss of proximal bone stock can be treated by a proximal femoral allograft or a tumor prosthesis. Wong and Gross (6) described the use of proximal structural allograft in 19 patients with periprosthetic femoral fractures who had a severe loss of bone stock. Fifteen patients were available for evaluation with a mean follow-up of 5 years. Thirteen patients showed good results. Two patients required additional surgery; 1 patient required plating for nonunion, and the other required further revision surgery. An alternate option in elderly patients is the use of a “megaprosthesis”: this allows immediate weight bearing and a faster rehabilitation. Even if this solution has a good outcome in elderly patients, the long-term survival of these implants is actually not so good: one series reported the survival of the prosthesis as only 64% at 12 years (7). Type C fractures are preferably treated with ORIF through the use of plates with screws and cerclage wires. These devices allow good primary stability of the implant, early recovery of weight bearing, and good final functional outcomes. Alternatively, it is possible to use retrograde femoral nailing for very distal fractures of the femur, located more than 6 cm from the tip of the stem. PHARMACOLOGICAL THERAPY In the periprosthetic femoral fractures the biology of the patient and the fracture lead to prolonged healing with
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bone union lasting up to 6 months. The consolidation of the fracture, indicated by pain levels, can take up to 2 years while the patient slowly recovers to their previous ambulatory status. Thus, any positive effect in enhancing consolidation could be considered a breakthrough in the management of these fragility fractures. The aim of fracture treatment is to restore the biomechanical properties of the fractured bone and to facilitate the return to the normal function of the affected limb. A growing body of evidence supports the notion that pharmaceutical agents active within the bone, and known to improve bone mass, may also be suitable agents for systemic enhancement of fracture repair. Anti-fracture agents typically prevent fractures by augmenting bone mass and enhancing skeletal integrity. These agents exert their effect by means of anti-catabolic or anabolic actions. Because fracture healing involves bone formation as well as bone resorption, it is reasonable to hypothesize that agents that affect these activities may also modulate skeletal repair. Alkhiary et al. (8) investigated the effects of recombinant human PTH(1-34) (teriparatide) on fracture healing in 270 rats that underwent standard closed femoral fractures and received doses of teriparatide similar to those shown to be effective in the treatment of osteoporosis in postmenopausal women. Using biomechanical tests, histomorphometry and quantitated computed tomography, these investigators demonstrated that daily systemic administration of both a 5 and a 30 mg/kg daily dose enhanced fracture healing by increasing bone mineral density, bone mineral content, and total osseous tissue volume. The PTH primarily enhances the earlier stages of endochondral bone repair by increasing chondrocyte recruitment and differentiation rate. Molecular analysis of the expression of extracellular matrix genes associated with chondrogenesis and osteogenensis showed that PTH(1-34)-treated fractures displayed a 3-times greater increase in chondrogenesis relative to osteogenesis over the period for the repair process (9). Based on these experimental studies, several clinical investigators have used teriparatide in the treatment of patients with fractures and reported individual cases or small case series. One clinical trial has been conducted investigating the use of teriparatide in postmenopausal women with distal radial fractures. The dorsally angulated distal radial fractures were treated with closed reduction and randomly selected for eight weeks of daily injections of either placebo or PTH(1-34 teriparatide) 20 mcg-40 mcg within ten days from the fracture. The time of healing was shorter in the teriparatide 20 mcg group than in the placebo group (p=0.006) (10). Strontium ranelate demonstrated an action on bone remodelling with inhibition of osteoclastic activity and stimulation of osteoblastic activity (11). This dual mechanism of activity is correlated to modulation of the Rank-L/OPG pathway through its affinity for calcium-sensing receptor on osteoblastic cells. In different animal models there is al-
Periprosthetic femoral fractures
so evidence of benefits of strontium ranelate on bone microarchitecture with increasing of cortical thickness and bone volume (12). Li et al. (13) investigated the effects of strontium ranelate on fracture healing in ovariectomized rats with fractured tibiae. Callus quality was assessed by radiographic, histological, micro-computerized tomography, and biomechanical examination at 4 and 8 weeks after fracture. The treatment with 625 mg/kg/day of strontium ranelate promoted the healing progress with an increased osteogenesis at 4 weeks and more mature and tightly arranged woven or lamellar bone at 8 weeks across the fracture gap. Based on these experimental studies, in 2009 we began our experience with pharmacological treatment in patients operated on for periprosthetic femoral fractures. This small case series included 5 patients with one year minimum follow-up. The average age of our cohort was 77 years (range 67-87 yrs). There were 3 females and 2 males, all of whom had sustained low-energy fractures. Before fracture, all were uncemented arthroplasties, of which 3 were primary and 2 were revision prostheses. In 3 patients the surgical treatment was ORIF using the Cable ready system in one case and the LCP system in the other two. Two patients were treated with implant revision using non-cemented modular stems. We used an anabolic drug (teriparatide or strontium ranelate) started within 7 days after surgery to accelerate fracture healing. Patients were kept at 50% weight bearing for the first 6 weeks then gradually increased until complete free weight bearing was achieved at the 3rd month. The quality of fixation, time of union, postoperative complications, pain, and functional outcome were recorded in all patients. Clinical and radiographic union was achieved by 4 months. All patients complained of some pain at follow-up, although in general all continued to improve by 12 months. All required walking aids at 3 months and showed progress with ambulation by 6 months. CONCLUSIONS The periprosthetic femoral fractures can be considered as “fragility fracture” because these occur more commonly in female patients with an average age of 70 years and with previous vertebral or methaphyseal fractures. Low-energy falls are the traumatic event that causes these fractures and every effort should be directed at identifying the risk factors for periprosthetic fracture and methods of prevention. Future studies should quantify the role played by subclinical osteolysis and whether alternative bearing couples have an impact on subsequent fracture. Investigations using bone mineral density studies in a
cohort of older patients who had primary total hip arthroplasty might help to ascertain whether those with lower bone mineral density are more at risk of this complication. It could be useful to reduce the risk of femoral fracture an adjuvant medical treatment for osteoporosis, fall prevention, or the use of primary long-stemmed femoral implants. Evidence from case reports and animal studies suggests that teriparatide and strontium ranelate improve bone microarchitecture and accelerate fracture healing. Further randomized controlled studies are necessary to investigate the clinical effectiveness of pharmacological treatments in periprosthetic fracture repair. REFERENCES 1. Lindahl H, Garellick G, Regner H, Herberts P, Malchau H. Three hundred and twenty-one periprosthetic femoral fractures. J Bone Joint Surg Am 2006; 88: 1215-22. 2. Swedish Hip Arthroplasty Register Annual Report 2008. Available at: www.jru.orthop.gu.se 3. Masri BA, Meek RM, Duncan CP. Periprosthetic fractures evaluation and treatment. Clin Orthop Relat Res 2004; (420): 80-95. 4. Wood GC, Naudie DR, McAuley J, McCalden RW. Locking compression plates for the treatment of periprosthetic femoral fractures around well-fixed total hip and knee implants. J Arthroplasty Sep. 2010 [Epub ahead of print]. 5. Springer BD, Berry DJ, Lewallen DG. Treatment of periprosthetic femoral fractures following total hip arthroplasty with femoral component revision. J Bone Joint Surg Am 2003; 85: 2156-62. 6. Wong P, Gross AE. The use of structural allograft for treating periprosthetic fractures about the hip and knee. Orthop Clin North Am 1999; 30: 259-64. 7. Malkani AL, Paiso JM, Sim FH. Proximal femoral replacement with a megaprosthesis. Instr Course Lect 2000; 49: 144-6. 8. Alkhiary YM, Gerstenfeld LC, Krall E. Enhancement of experimental fracture-healing by systemic administration of recombinant human parathyroid hormone (PTH 1-34). J Bone Joint Surg A 2005; 87: 731-41. 9. Barnes GL, Kakar S, Vora S, Morgan EF, Gerstenfeld LC, Einhorm TA. Stimulation of fracture-healing with systemic intermittent parthyroid hormone treatment. J Bone Joint Surg Am 2008; 90: 120-7. 10. Aspenberg P, Genant HK, Johansson T et al. Teriparatide for acceleration of fracture repair in humans: a prospective, randomized, double-blind study of 102 postmenopausal women with distal radial fractures. J Bone Miner Res 2010; 25: 404-14. 11. Marie PJ. Strontium ranelate in osteoporosis and eyon: identifying molecular targets in bone cell biology. Mol Int 2010; 10: 305-12. 12. Bain SD, Jerome C, Shen V, Dupin-Roger I, Ammann P. Strontium ranelate improves bone strength in ovariectomized rat by positively influencing bone resistance determinants. Osteoporos Int 2009; 20: 1417-28. 13. Li YF, Luo E, Feng G, Zhu SS, Li JH, Hu J. Systemic treatment with strontium ranelate promotes tibial fracture healing in ovariectomized rats. Osteoporos Int 2010; 21: 1889-97.
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