Drs Saito, Tokuhashi, Ishii, Mori, Hosaka, Ryu, and Suzuki are from the Department of Orthopedic Surgery, Nihon University School of Medicine, Tokyo, Japan.
Drs Saito, Tokuhashi, Ishii, Mori, Hosaka, Ryu, and Suzuki have no relevant financial relationships to disclose.
Correspondence should be addressed to: Shu Saito, MD, Department of Orthopedic Surgery, Nihon University School of Medicine, 30-1 Oyaguchi, Kami-machi, Itabashi-Ku, Tokyo 173-8610 Japan (email@example.com,jp).
In the majority of case reports, stress fractures of the femoral component have predominantly affected the medial condyle, following uncemented implantation of fixed-bearing knees. In this case, failure of bone ingrowth in uncemented components, higher body mass index, and a higher athletic activity led to fatigue fracture of the femoral components.
A 75-year-old woman (height, 158 cm; weight, 72 kg; body mass index, 29.2) had undergone one-stage bilateral total knee arthroplasty (TKA) for osteoarthritis (Figure 1) 11 years previously at our institution. Surgery was performed using an uncemented Flexible Nichidai Knee system (Nakashima Medical Inc, Okayama, Japan), which is a cruciate-retaining prosthesis. The femoral component of cobalt-chromium alloy and the tibial component of titanium alloy had a 1-mm fiber-mesh coating layer. Equal tension of the collateral ligaments and normal mechanical axis were achieved at the primary procedure.
Figure 1: Preoperative weight-bearing standing AP radiographs of the right (A) and left (B) knees show severe destruction of the articular cartilage in the medial compartment with a varus deformity.
She had a satisfactory clinical result, with a pain-free knee and range of motion from 0° to 110°. She had regular clinical and radiographic follow-ups at 3, 6, and 12 months after surgery and then at 1-year intervals, without any change in her clinical and radiological results. She had a satisfactory recovery and enjoyed playing badminton 1 hour daily as an ardent lover of the sport.
At 8 years postoperatively, she started complaining of mild pain in both of her knees. The pain gradually increased, and at 11 years postoperatively, she had difficulty walking and required a cane.
On examination, neither knee was swollen or tender. Range of motion for both knees was 0° to 110°. Complaints of severe pain and a slight varus deformity with weight bearing were observed in both knees. Knee Society knee and function scores1 were 49 and 35, respectively.
Anteroposterior radiographs showed narrowing of the medial joint space, indicating wear of the polyethylene insert. Lateral radiographs showed signs of broken implants in both knees. There were no signs of gross implant loosening or osteolysis (Figure 2).
Figure 2: Radiographs of the right (A, B) and left (C, D) knees 11 years after the index arthroplasty show narrowing of the medial joint space and the broken implant.
One-stage revision surgery was performed, and the knees were converted to cemented implants. At surgery, the previous skin incision was extended, and a medial parapatellar approach was performed to check for component stability. A transverse fracture of the medial condyle of the femoral component was noted at the junction between the trochlear flange and the medial condyle area in both knees. The polyethylene insert showed mild wear at medial middle part (Figure 3). The remaining femoral component and tibial tray were both stable.
Figure 3: Photograph showing the retrieved femoral components. A transverse fracture of the medial condyle of the femoral component was noted at the junction between the trochlear flange and the medial condyle area in both knees, and the polyethylene insert showed mild wear at medial middle part.
After removal of the femoral component and polyethylene insert, a thin layer of fibrous tissue was found interposed between the bone and metal under the fracture area. There were no signs of focal osteolysis. Bone ingrowth was seen on the porous surface of the femoral component, except in the fractured area. A cemented posterior-stabilized Flexible Nichidai Knee was implanted; bone grafts were not necessary.
The patient’s recovery was uneventful, and she regained satisfactory pain-free knee function. One year postoperatively, the patient walked without a cane, and her range of motion was 0° to 110°. Knee Society knee and function scores were 89 and 90 points, respectively. Radiographs showed correct alignment with no loosening of the prostheses (Figure 4).
Figure 4: AP radiographs of the right (A) and left (B) knees after revision with cemented posterior-stabilized prostheses showed correct alignment with no loosening.
Occasional fractures of the tibial metal component in resurfacing designs have been reported.2,3 However, fatigue fracture of the femoral component is rare following TKA. The femoral component fracture rate has been reported to range from 0.5% to 3.3%.4–7 Whiteside et al5 reported the rate of failure to be 0.5% in 6172 knees with the double-bead layer Ortholoc II prosthesis (Dow Corning Wright, Arlington, Tennessee). Wada et al6 reported a rate of 3.3%, with 3 femoral component fractures among 92 small-size Ortholoc II prostheses (Table).
Table: Femoral Component Stress Fractures Reported in the Literature Following Primary Total Knee Arthroplasty
For our case, the rate of femoral component fatigue fracture among 87 uncemented cruciate-retaining Flexible Nichidai Knee was 2.2%, whereas among our cemented TKAs (3260 cruciate-retaining and 2162 posterior-stabilizing designs), the rate of femoral component fatigue fracture was zero. To our knowledge, no bilateral fatigue fractures have been reported in literature. The reported time interval between the index arthroplasty and femoral component fracture has ranged from 20 months to 11 years.4–7 In our case, bilateral fatigue fracture of the femoral components occurred 11 years after one-stage bilateral primary implantation.
Several reports attributed the fracture of the femoral component to specific design features of the uncemented double-bead Ortholoc II prosthesis4–7; no fatigue fracture with other types of femoral components was reported in the literature for several years. However, 2 fractures of the femoral component of the Genesis II knee prosthesis (Smith & Nephew, Memphis, Tennessee) were reported by Michos et al8 in 2006 and Luring et al9 in 2007. Duffy et al10 reported 2 femoral component fractures in the PFC prosthesis (DePuy, Raynham, Massachusetts) in 2007. These data showed the fatigue fractures of the femoral component have predominantly involved the medial condyle, following uncemented implantation of fixed-bearing knees. However, 3 fractures of the femoral component of the mobile-bearing Low Contact Stress (LCS) prosthesis (DePuy) were reported by Huang et al11 in 1999, Han et al12 in 2009, and Lemaire13 in 2010.
In the majority of case reports, the femoral components were uncemented implantations in primary TKAs.4–13 It may be difficult to achieve full and stable contact with bone at the junction of the beveled surfaces of the femoral component, which can lead to failure of bone ingrowth in uncemented components. In our case, a thin layer of fibrous tissue was found interposed between bone and metal under the fracture area, although there were no signs of focal osteolysis.
Design features of the prostheses have in specific cases contributed to the occurrence of fatigue fractures. In a study of 31 Ortholoc II prostheses with double-bead coating, Whiteside et al5 found that 29 fractures happened at the medial condyle where the metal thickness was only 3 mm. This proved insufficient with respect to the local loads and stresses. In our case, the fracture area was located at the junction between the trochlear flange and the medial condyle in both knees, with a 1-mm fiber-mesh coating layer, where the metal thickness was only 3 mm, similar to that found in the Ortholoc II prostheses.
In our patient, the fracture predominantly affected the medial condyle of the femoral component. This may be related to the higher load share of the medial knee compartment, which may be even greater if the knee has been realigned with a slight varus deformity.
In the majority of the case reports, there were no differences in the patients’ gender. However, patients’ age ranged from 51 to 75 years (average, 58.1 years) at the time of the index procedure.4–13 The average age was younger than in most TKA cohort studies, which is typically 70 years. Younger age is presumably associated with a higher activity level resulting in higher stresses on the implants.
Many factors contribute to the fatigue fracture of the femoral components. In our case, failure of bone ingrowth in uncemented components, higher body mass index, and higher athletic activity led to fatigue fracture of the femoral components.
- Insall JN, Dorr LD, Scott RD, Scott WN. Rationale of the Knee Society clinical rating system. Clin Orthop Relat Res. 1989; (248):13–14.
- Morrey BF, Chao EY. Fracture of the porous-coated metal tray of a biologically fixed knee prosthesis: report of a case. Clin Orthop Relat Res. 1988; (228):182–189.
- Altintas F, Sener N, Ugutmen E. Fracture of the tibial tray after total knee arthroplasty. J Arthroplasty. 1999; 14(1):112–114. doi:10.1016/S0883-5403(99)90212-7 [CrossRef]
- Cook SD, Thomas KA. Fatigue failure of noncemented porous-coated implants: a retrieval study. J Bone Joint Surg Br. 1991; 73(1):20–24.
- Whiteside LA, Fosco DR, Brooks JG Jr, . Fracture of the femoral component in cementless total knee arthroplasty. Clin Orthop Relat Res. 1993; (286):71–77.
- Wada M, Imura S, Bo A, Baba H, Miyazaki T. Stress fracture of the femoral component in total knee replacement: a report of 3 cases. Int Orthop. 1997; 21(1):54–55. doi:10.1007/s002640050118 [CrossRef]
- Swarts E, Miller SJ, Keogh CV, Lim G, Beaver RJ. Fractured Whiteside Ortholoc II knee components. J Arthroplasty. 2001; 16(7):927–934. doi:10.1054/arth.2001.25508 [CrossRef]
- Michos J, Rallis J, Fassoulas A. Fracture of femoral component in a resurfacing total knee arthroplasty. J Arthroplasty. 2006; 21(7):1068–1071. doi:10.1016/j.arth.2005.10.024 [CrossRef]
- Luring C, Perlick L, Schubert T, Tingart M. A rare cause for knee pain: fracture of the femoral component after TKA: a case report. Knee Surg Sports Traumatol Arthrosc. 2007; 15(6):756–757. doi:10.1007/s00167-006-0210-y [CrossRef]
- Duffy GP, Murray BE, Trousdale RR. Hybrid total knee arthroplasty analysis of component failures at an average of 15 years. J Arthroplasty. 2007; 22(8):1112–1115. doi:10.1016/j.arth.2007.04.007 [CrossRef]
- Huang CH, Yang CY, Cheng CK. Fracture of the femoral component associated with polyethylene wear and osteolysis after total knee arthroplasty. J Arthroplasty. 1999; 14(3):375–379. doi:10.1016/S0883-5403(99)90066-9 [CrossRef]
- Han CD, Han CW, Yang IH. Femoral component fracture due to osteolysis after cemented mobile-bearing total knee arthroplasty. J Arthroplasty. 2009; 24(2):323.e7–12. doi:10.1016/j.arth.2008.03.003 [CrossRef]
- Lemaire R. Fatigue fracture of the femoral component in a mobile bearing knee prosthesis. Acta Orthop Belg. 2010; 76(2):274–281.
Femoral Component Stress Fractures Reported in the Literature Following Primary Total Knee Arthroplasty
|Author||Implant||Bearing Type||Medial/Lateral||Size||Fixation||PE||Patient/Age, y||Delay|
|Cook & Thomas4||Ortholoc IIa||Fixed||Medial||NA||Uncemented||NA||M/69||20 months|
|Whiteside et al5||Ortholoc IIa||Fixed||Medial||Large||Uncemented||NA||M/64||25 months|
|Ortholoc IIa||Fixed||Medial||Large||Uncemented||NA||M/64||37 months|
|Ortholoc IIa||Fixed||Medial||Extra large||Uncemented||NA||M/64||40 months|
|Ortholoc IIa||Fixed||Medial||Medium||Uncemented||NA||F/59||43 months|
|Wada et al6||Ortholoc IIa||Fixed||Medial||Small||Cemented||NA||F/71||32 months|
|Ortholoc IIa||Fixed||Medial||Small||Uncemented||NA||F/72||52 months|
|Ortholoc IIa||Fixed||Medial||Small||Uncemented||NA||F/62||73 months|
|Swarts et al7||Ortholoc IIa||Fixed||Medial||NA||Uncemented||NA||M/73||5 years|
|Ortholoc IIa||Fixed||Medial||NA||Uncemented||NA||M/71||4 years|
|Ortholoc IIa||Fixed||Medial||NA||Uncemented||NA||F/75||7 years|
|Ortholoc IIa||Fixed||Medial||NA||Uncemented||NA||F/69||7 years|
|Ortholoc IIa||Fixed||Medial||NA||Uncemented||NA||F/51||10 years|
|Ortholoc IIa||Fixed||Lateral||NA||Uncemented||NA||M/70||11 years|
|Michos et al8||Genesis IIb||Fixed||Medial||Medium||Uncemented||NA||F/72||3 years|
|Luring et al9||Genesis IIb||Fixed||Medial||NA||Cemented||10 mm||M/68||9 years|
|Duffy et al10||PFCc||Fixed||Medial||Size 6||Uncemented||NA||M||NA|
|Huang et al11||LCS RPd||Mobile||Medial||Large||Uncemented||10 mm||M/63||42 months|
|Han et al12||LCS APGd||Mobile||Trochlea||NA||Cemented||10 mm||M/58||43 months|
|Lemaire13||LCS meniscald||Mobile||Medial||Standard +||Uncemented||10 mm||F/58||78 months|
|Saito et al (current study)||FNKe||Fixed||Medial||Medium||Uncemented||7 mm||F/64||11 years|