Copyright © SLACK inCorporAted

n Case Report

abstract

Modular Hip Implant Fracture at the Stem-Sleeve Interface

Thomas Parisi, mD, JD; Brian Burroughs, mD; Young-min Kwon, mD, PhD

The use of modular implants in femoral stem design has grown increasingly popular over the last decade because of the theoretical advantage of more flexibility and optimization of femoral anteversion, limb length, and femoral component offset. With the benefit of increased surgical flexibility, however, modularity also carries the theoretical risks of fretting at the modular surfaces, sequelae of wear debris, and possible failure and fracture of the stem at the modular junction. Indeed, there have been an increasing number of reports of modular implants failing due to fracture at modular junctions. The S-ROM prosthesis (DePuy Orthopaedics, Inc, Warsaw, Indi-ana), however, has a stellar clinical record and has been used with good results in both primary and revision total hip arthroplasty. Only a single case of S-ROM failure at the stem-sleeve interface has been reported in the orthopedic literature. The aim of this case report was to present a succinct history of proximal modularity in total hip arthroplasty and to describe the only known case of this type of catastrophic failure in an S-ROM prosthesis with a metal-on-metal bearing. Despite a low level of serum metal ions on presentation, scanning electron microscopy showed findings consistent with corrosive processes and pseudotumor was seen at revision surgery. [Orthopedics. 2015; 38(3):e234-e239.]

The authors are from the Orthopaedic Department, Massachusetts General Hospital, Boston, Mas-sachusetts.

The authors have no relevant financial relationships to disclose.Correspondence should be addressed to: Thomas Parisi, MD, JD, Orthopaedic Department, Mas-

sachusetts General Hospital, 55 Fruit St, Boston, MA 02114 (tparisi@partners.org). Received: April 27, 2014; Accepted: June 24, 2014.doi: 10.3928/01477447-20150305-91

e234

MARCH 2015 | Volume 38 • Number 3

n Case Report

The use of modular implants in femoral stem design has grown increasingly popular over the last

decade because of the theoretical advan-tage of more flexibility and optimization of femoral anteversion, limb length, and femoral component offset.1 The S-ROM prosthesis (DePuy Orthopaedics, Inc, Warsaw, Indiana), a modification of the original Sivash Stem (Joint Medical Prod-ucts, New Brunswick, New Jersey), is a pioneering proximal modular stem that first came to market in 1982.2 Since its introduction, the S-ROM prosthesis has provided stellar clinical performance and is used in both primary and revision total hip arthroplasty.2 Although several ex-amples of other modular implant failures have been reported,1,3-10 only a single case of failure of an S-ROM prosthesis at the stem-sleeve interface has been reported.11 A review of the US Food and Drug Ad-ministration adverse event report database showed at least 6 other reported fractured necks or fractures at the neck-sleeve inter-face with this device design since its in-troduction.12 The current report is the only known case of this type of metal-on-metal bearing failure.

Case RepoRtA 50-year-old man underwent pri-

mary total arthroplasty of the right hip in January 2007 after failed conservative treatment of degenerative osteoarthritis. The patient received an 11×16×150-mm modular femoral stem with a neck length of 36+6 mm and a 16B-LRG ZTT proxi-mal femoral sleeve (DePuy Orthopaedics, Inc). The femoral head was an S-ROM 36-mm M cobalt-chromium head with 6 additional mm of neck length (DePuy Orthopaedics, Inc), and the acetabulum was a Pinnacle Sector II size 56 cup (DePuy Orthopaedics, Inc) with a Pin-nacle 36×56-mm metal insert (DePuy Or-thopaedics, Inc). The procedure was per-formed through a posterolateral approach, and no complications occurred intra- or postoperatively. Approximately 3.5 years

after implantation, the patient had pain in the operative hip and returned to see the original surgeon. Because of concerns about the metal-on-metal articulation of the prosthesis, revision surgery was rec-ommended. However, the patient decided against that option because he worked as a self-employed brick mason and could not take the time off of work. He was active for another 2 years, at which point he present-ed to the authors’ institution for a second opinion regarding his pain. At presenta-tion, 5.5 years postoperatively, his height was 6 feet and his weight was 240 lb, for a body mass index of 32.5. His pain oc-curred mainly in the groin and the anterior and lateral thigh. Pain was worsened by activity, walking more than 6 city blocks,

and improved with nonsteroidal anti-in-flammatory drugs. He had no history of trauma and had no infectious symptoms. Harris Hip Score was 56 on the operative leg and 88 on the contralateral side. The EuroQol 5D score was 0.69 and 82, and University of California, Los Angeles, ac-tivity score was 5. Radiographs showed an S-ROM prosthesis, with a metal-on-metal bearing surface, with good bony ingrowth of both the acetabular and femoral compo-nents (Figure 1A).

At presentation, white blood cell count was 6.0×109/L (reference range, 4.5-11.0×109/L), erythrocyte sedimentation rate was 7 mm/h (reference range, 0-13 mm/h), and C-reactive protein level was 2.1 mg/L (reference range, <8.0 mg/L).

Figure 1: Anteroposterior radiograph of the right hip at the time of initial consultation for right hip pain, approximately 5.5 years after total hip arthroplasty. A metal-on-metal bearing surface with good bony ingrowth of both acetabular and femoral components (A). Sagittal (B) and coronal (C) magnetic resonance imaging sequences showing thickened soft tissue with decreased signal intensity near the neck of the femoral component and heterogeneous signal in the trochanteric region, suggestive of osteolysis, but no fluid collection or evidence of pseudotumor.

e235

Copyright © SLACK inCorporAted

n Case Report

Serum metal ion levels were obtained and showed a cobalt level of 1.5 μg/L and a chromium level of 0.8 μg/L. Metal artifact reduction sequence magnetic resonance image (MRI) obtained at that time showed thickened soft tissue with decreased sig-nal intensity near the neck of the femo-ral component and heterogeneous signal in the trochanteric region, suggestive of osteolysis (Figures 1B-C). The pa-tient elected to be monitored closely. Six months later, he returned for follow-up with no progression in pain, stable find-ings on radiographs, white blood cell count of 6.10×109/L (reference range, 4.5-11.0×109/L), erythrocyte sedimenta-tion rate of 8 mm/h (reference range, 0-13 mm/h), C-reactive protein level of 1.6

mg/L (reference range, <8.0 mg/L), co-balt level of 1.0 μg/L, and chromium level of 1.0 μg/L. The decision was made to continue annual surveillance. The patient returned 1 year later with no progression in symptoms. Repeat metal artifact reduc-tion sequence MRI and serum metal ion levels (cobalt, 1.0 μg/L; chromium, 0.9 μg/L) showed no significant changes.

Approximately 7 years postoperatively, the patient presented to the emergency de-partment with acute onset of “feeling his hip gave out,” with marked pain and inabil-ity to bear weight. This episode was atrau-matic and occurred while the patient was walking through a convenience store. Be-fore the acute incident, he had no increase in pain and no mechanical symptoms, such

as grinding, clicking, or squeaking, that had been cited in other cases of component failure.1,3,4,7,8,11 Radiographs performed at the time showed a fracture of the femoral stem at the sleeve-stem interface (Figure 2). Laboratory values on admission showed a white blood cell count of 8.5×109/L (ref-erence range, 4.5-11.0×109/L), erythrocyte sedimentation rate of 7 mm/h (reference range, 0-13 mm/h), and C-reactive pro-tein level of 1.31 mg/L (reference range, <8.0 mg/L). The cobalt level was 0.8 μg/L, chromium level was 0.9 μg/L, and titanium level was 36 μg/L.

The patient underwent revision arthro-plasty 2 days after admission. A postero-lateral incision was used. The proximal portion of the prosthesis with the femoral head was easily removed after dislocation, and a transverse stem fracture was noted several millimeters below the proximal end of the metaphyseal sleeve (Figure 3). A combination of high-speed burrs was used to debride bone around the proximal metaphyseal sleeve, after which a vice grip and a slap hammer were used to re-move the proximal sleeve and the attached remaining portion of the femoral prosthe-sis. Based on the remaining metaphyseal femoral bone stock deficiency and signifi-cant necrosis of periprosthetic soft tissues involving the abductor muscles, the deci-sion was made to use a revision stem with midstem modularity to optimize stem fixation and stability.

After the stem was removed, the femo-ral canal was prepared and a Stryker res-toration modular 155-mm conical distal stem was placed (Stryker Orthopaedics, Mahwah, New Jersey) with a 23-mm cal-car body. The metal head was replaced with a Stryker Biolox 36-mm ceramic head with a +2.5-mm neck length. The acetabular cup appeared well fixed in the operating room; however, the metal liner from the acetabulum was removed and a 36-mm DePuy Pinnacle polyethylene lin-er was placed. Postoperatively, the patient did well and was discharged on postopera-tive day 4.

Figure 2: Macroscopic examination showing fretting and corrosion of the fractured surface (A, B). Scan-ning electron microscopy image of the anterolateral fracture surface showing the initiation site of the fracture adjacent to a large pit, with a clamshell pattern radiating from the corroded area (C). Scanning electron microscopy image of the center of the mating surface showing corrosion, with scalloping and pitting (D).

e236

MARCH 2015 | Volume 38 • Number 3

n Case Report

Although preoperative MRI showed no obvious adverse tissue reaction, at the time of surgery, significant thickened necrotic periprosthetic pseudocapsule involving the abductor muscles was found. This was debrided and was found on pathologic ex-amination to contain necrotic tissue and evidence of reactive debris. Additionally, examination of the fracture surfaces of the implant at the time of surgery showed areas of blackened surface that were con-cerning for corrosive change.

Evaluation was performed with a Phil-ips FEI XL-30 (FEI Company, Hillsboro, Oregon) scanning electron microscope. Examination of the fracture surfaces showed severe corrosive changes con-sisting of pitting and scalloping. A clear clamshell pattern characteristic of fatigue fracture radiated from the corroded area on the anterolateral surface of the fracture site. Energy dispersive x-ray spectroscopy showed high levels of oxygen and calcium in addition to titanium and aluminum at the fracture surface (Figure 2 and Figure 4).

DisCussionSince its release, the S-ROM prosthe-

sis has offered stellar clinical performance and has been prominently used for more than 30 years in complicated and uncom-plicated revision and primary total hip ar-throplasty.2 Although modular prostheses allow for considerable surgical flexibility, there was initial concern and skepticism about the S-ROM stem because of pos-sible fretting of the modular surfaces, se-quelae of wear debris, and possible failure and fracture of the stem at the modular junction.13 However, except for 1 case re-port11 and several possible instances in the US Food and Drug Administration data-base12 over all years of use, the S-ROM has had no other reports of catastrophic failure or fracture at the modular junction or neck.2,11,12

Fracture of femoral components is a rare complication in total hip arthro-plasty, with Charnley14 estimating the

Figure 3: Anteroposterior radiograph of the right hip at the time of presentation to the emergency depart-ment 7 years after total hip arthroplasty. The femoral stem is fractured at the stem-sleeve interface (A). The retrieved stem showing a fracture several millimeters below the proximal end of the metaphyseal sleeve (B). Macroscopic evidence of fatigue wear and corrosion (C).

Figure 4: Anteroposterior (A) and oblique (B) radiographs of the right hip approximately 6 months after revision.

A B

e237

Copyright © SLACK inCorporAted

n Case Report

incidence of stem fractures in implants before forged cobalt-chromium molyb-denum and titanium alloys to be 0.23%. The prevalence increased to 6.0% in men weighing more than 75 kg,14 and the inci-dence with other designs may be as high as 11.0%.15 Most femoral component fractures reportedly occur in the stem; however, fractures of the neck have been reported in modular designs.1,3-9,11,13 The locations of these fractures range from the proximal head-neck junction to the neck-stem junction, and factors contributing to fracture include corrosion and fretting at the modular interface16,17 or head-neck junction,18 defects in welding the neck to the prosthesis,19 and high use of laser etching in the region.20

There are examples of fracture in the modular neck of modern hip im-plants. Most prominently reported is the Profemur-Z (Wright Medical Technology, Arlington, Tennessee), which in the Aus-tralian market has shown an unacceptably high failure rate of 11.2% at the modular stem-body tapered junction.21 Similarly designed modular implants have fractured 1 to 2 mm proximal to the body-stem junction, and the cause is believed to be a repetitive bending moment, leading to fracture initiation, propagation, and ulti-mate failure.22

The previous case report of failure of an S-ROM was a metal-on-polyethylene articulation. Macroscopically, blackened areas of the implant showed areas of cor-rosion, and further microscopic analysis performed by DePuy Orthopaedics, Inc, showed evidence of fatigue fracture sec-ondary to micromotion and cyclic loading at the stem-sleeve interface.11

In the current case, despite a low level of metal ions on presentation and at the time of fracture and no obvious pseudo-capsule on MRI, there was evidence of macroscopic corrosion denoted by ar-eas of blackened surface on the implant. An area of thickened pseudocapsule was debrided at the time of surgery and was found on pathologic examination to con-

tain necrotic tissue and evidence of debris reaction. Scanning electron microscopic evaluation also showed scalloping and pit-ting, consistent with a corrosive process causing weakening of the implant and susceptibility to cyclic fatigue fracture.

ConClusionThis case report, although describing

a seemingly extremely rare occurrence in the S-ROM stem, reaffirms the trade-off between versatility during implantation and the long-term robustness of modular implants. This implant had a metal-on-metal articulation, possibly increasing the risk of corrosive processes at the modular junction that could result in failure. How-ever, the use of metal-on-metal devices has decreased significantly, with only 1% of hip resurfacing procedures and 2% of large heads using metal-on-metal total hip replacements.23 Although double modular devices seem to be at higher risk for implant fracture, any modular junc-tion can have substantial fretting and cor-rosion and subsequent fracture. Although diagnostic tools such as metal ion levels and MRI are useful, these may not be able to predict catastrophic fractures. Howev-er, a differential diagnosis of taper corro-sion should be considered when evaluat-ing symptomatic patients with a modular implant.

RefeRenCes 1. Wright G, Sporer S, Urban R, Jacobs J. Frac-

ture of a modular femoral neck after total hip arthroplasty: a case report. J Bone Joint Surg Am. 2010; 92(6):1518-1521.

2. Spitzer AI. The S-ROM cementless femoral stem: history and literature review. Orthope-dics. 2005; 28(9 suppl):s1117-s1124.

3. Dangles CJ, Altstetter CJ. Failure of the mod-ular neck in a total hip arthroplasty. J Arthro-plasty. 2010; 25(7):1169.e5-e7.

4. Morley D, Starks I, Lim J. A case of a C-stem fracture at the head-neck junction and a review of the literature. Case Rep Orthop. 2012; 2012:158604.

5. Wilson DA, Dunbar MJ, Amirault JD, Farhat Z. Early failure of a modular femoral neck to-tal hip arthroplasty component: a case report. J Bone Joint Surg Am. 2010; 92(6):1514-

1517.

6. Atwood SA, Patten EW, Bozic KJ, Pruitt LA, Ries MD. Corrosion-induced fracture of a double-modular hip prosthesis: a case report. J Bone Joint Surg Am. 2010; 92(6):1522-1525.

7. Skendzel JG, Blaha JD, Urquhart AG. Total hip arthroplasty modular neck failure. J Ar-throplasty. 2011; 26(2):338 e331-e334.

8. Ellman MB, Levine BR. Fracture of the modular femoral neck component in total hip arthroplasty. J Arthroplasty. 2013; 28(1):196. e191-e195.

9. Sotereanos NG, Sauber TJ, Tupis TT. Modu-lar femoral neck fracture after primary to-tal hip arthroplasty. J Arthroplasty. 2013; 28(1):196.e7-e9.

10. Lam LO, Stoffel K, Kop A, Swarts E. Cata-strophic failure of 4 cobalt-alloy Omnifit hip arthroplasty femoral components. Acta Or-thop. 2008; 79(1):18-21.

11. Mehran N, North T, Laker M. Failure of a modular hip implant at the stem-sleeve inter-face. Orthopedics. 2013; 36(7):e978-e981.

12. U.S. Food and Drug Administration. MAUDE (Manufacturer and User Facility Device Experience) database. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/ cfMAUDE/search.cfm. Accessed December 21, 2013.

13. Cook SD, Manley MT, Kester MA, Dong NG. Torsional resistance and wear of a modular sleeve-stem hip system. Clin Mater. 1993; 12(3):153-158.

14. Charnley J. Fracture of femoral prostheses in total hip replacement: a clinical study. Clin Orthop Relat Res. 1975; (111):105-120.

15. Martens M, Aernoudt E, de Meester P, et al. Factors in the mechanical failure of the femo-ral component in total hip prosthesis: report of six fatigue fractures of the femoral stem and results of experimental loading tests. Acta Orthop Scand. 1974; 45(5):693-710.

16. Viceconti M, Baleani M, Squarzoni S, Toni A. Fretting wear in a modular neck hip pros-thesis. J Biomed Mater Res. 1997; 35(2):207-216.

17. Viceconti M, Ruggeri O, Toni A, Giunti A. Design-related fretting wear in modular neck hip prosthesis. J Biomed Mater Res. 1996; 30(2):181-186.

18. Gilbert JL, Buckley CA, Jacobs JJ, Bertin KC, Zernich MR. Intergranular corrosion- fatigue failure of cobalt-alloy femoral stems: a failure analysis of two implants. J Bone Joint Surg Am. 1994; 76(1):110-115.

19. Aspenberg P KL, Persson L, Onnerfalt R. Fracture of hip prostheses due to inadequate welding. Acta Orthop Scand. 1987; (58):479-482.

20. Lee EW, Kim HT. Early fatigue failures of cemented, forged, cobalt-chromium femoral

e238

MARCH 2015 | Volume 38 • Number 3

n Case Report

stems at the neck-shoulder junction. J Arthro-plasty. 2001; 16(2):236-238.

21. Australian Orthopaedic Association. Na-tional Joint Replacement Registry: annual report. Adelaide, Australia: Australian Or-thopaedic Association; 2009.

22. Lakstein D, Eliaz N, Levi O, et al. Fracture of cementless femoral stems at the mid-stem junction in modular revision hip arthro-plasty systems. J Bone Joint Surg Am. 2011; 93(1):57-65.

23. National Joint Registry for England, Wales,

and Northern England 10th Annual Re-port 2013. http://www.njrcentre.org.uk/njrcentre/Portals/0/Documents/England/Reports/10th_annual_report/NJR10th Annual Report2013B.pdf. Accessed June 14, 2014.

e239