Original Research

Radiographically Silent Loosening of the Acetabular Component in Hip Arthroplasty

Am J Orthop. 2015 September;44(9):406-410

Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of total hip arthroplasty (THA).

We conducted a study to determine the incidence of loose acetabular components that did not show frank signs of loosening on either plain radiography or computed tomography (CT), or radiographically silent loosening (RSL). In this retrospective study, we evaluated patients who underwent revision THA and were evaluated with plain radiography and CT between 2000 and 2012. Any patient with imaging that showed signs of component movement was excluded.

Of the 104 patients who met the study inclusion criteria, 17 (16.3%) met the criteria for RSL of the acetabular shell. Patients with RSL presented at a similar age (P = .961) and with a similar sex profile (P = .185) compared with patients with stable acetabular components and were more likely to present with pain (P = .0487).

Acetabular components may be loose even if there is no evidence of component migration on radiographic studies. Surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.

PDF Download

References

1. Milošev I, Kovač S, Trebše R, Levašič V, Pišot V. Comparison of ten-year survivorship of hip prostheses with use of conventional polyethylene, metal-on-metal, or ceramic-on-ceramic bearings. J Bone Joint Surg Am. 2012;94(19):1756-1763.

2. D’Antonio JA, Capello WN, Naughton M. Ceramic bearings for total hip arthroplasty have high survivorship at 10 years. Clin Orthop Relat Res. 2012;470(2):373-381.

3. Dowd JE, Sychterz CJ, Young AM, Engh CA. Characterization of long-term femoral-head-penetration rates. Association with and prediction of osteolysis. J Bone Joint Surg Am. 2000;82(8):1102-1107.

4. Orishimo KF, Claus AM, Sychterz CJ, Engh CA. Relationship between polyethylene wear and osteolysis in hips with a second-generation porous-coated cementless cup after seven years of follow-up. J Bone Joint Surg Am. 2003;85(6):1095-1099.

5. Harris WH. Wear and periprosthetic osteolysis: the problem. Clin Orthop Relat Res. 2001;(393):66-70.

6. Holt G, Murnaghan C, Reilly J, Meek RM. The biology of aseptic osteolysis. Clin Orthop Relat Res. 2007;(460):240-252.

7. Catelas I, Jacobs JJ. Biologic activity of wear particles. Instr Course Lect. 2010;59:3-16.

8. Paprosky WG, Nourbash P, Gill P. Treatment of progressive periacetabular osteolysis: cup revision versus liner exchange and bone grafting. Paper presented at: Annual Meeting of the American Academy of Orthopaedic Surgeons; February 4-8, 1999; Anaheim, CA.

9. Engh CA Jr, Claus AM, Hopper RH Jr, Engh CA. Long-term results using the anatomic medullary locking hip prosthesis. Clin Orthop Relat Res. 2001;(393):137-146.

10. Maloney WJ, Peters P, Engh CA, Chandler H. Severe osteolysis of the pelvic in association with acetabular replacement without cement. J Bone Joint Surg Am. 1993;75(11):1627-1635.

11. Claus AM, Engh CA Jr, Sychterz CJ, Xenos JS, Orishimo KF, Engh CA Sr. Radiographic definition of pelvic osteolysis following total hip arthroplasty. J Bone Joint Surg Am. 2003;85(8):1519-1526.

12. Puri L, Wixson RL, Stern SH, Kohli J, Hendrix RW, Stulberg SD. Use of helical computed tomography for the assessment of acetabular osteolysis after total hip arthroplasty. J Bone Joint Surg Am. 2002;84(4):609-614.

13. Stulberg SD, Wixson RL, Adams AD, Hendrix RW, Bernfield JB. Monitoring pelvic osteolysis following total hip replacement surgery: an algorithm for surveillance. J Bone Joint Surg Am. 2002;84(suppl 2):116-122.

14. Massin P, Schmidt L, Engh CA. Evaluation of cementless acetabular component migration. An experimental study. J Arthroplasty. 1989;4(3):245-251.

15. Park KS, Yoon TR, Song EK, Lee KB. Results of isolated femoral component revision with well-fixed acetabular implant retention. J Arthroplasty. 2010;25(8):1188-1195.

16. Egawa H, Ho H, Hopper RH Jr, Engh CA Jr, Engh CA. Computed tomography assessment of pelvic osteolysis and cup–lesion interface involvement with a press-fit porous-coated acetabular cup. J Arthroplasty. 2009;24(2):233-239.

17. Haidukewych GJ. Osteolysis in the well-fixed socket: cup retention or revision? J Bone Joint Surg Br. 2012;94(12):65-69.

18. Stulberg BN, Della Valle AG. What are the guidelines for the surgical and nonsurgical treatment of periprosthetic osteolysis? J Am Acad Orthop Surg. 2008;16(suppl 1):S20-S25.

19. Berger RA, Quigley LR, Jacobs JJ, Sheinkop MB, Rosenberg AG, Galante JO. The fate of stable cemented acetabular components retained during revision of a femoral component of a total hip arthroplasty. J Bone Joint Surg Am. 1999;81(12):1682-1691.

20. Temmerman OP, Raijmakers PG, Deville WL, Berkhof J, Hooft L, Heyligers IC. The use of plain radiography, subtraction arthrography, nuclear arthrography, and bone scintigraphy in the diagnosis of a loose acetabular component of a total hip prosthesis: a systematic review. J Arthroplasty. 2007;22(6):818-827.

21. Temmerman OP, Raijmakers PG, David EF, et al. A comparison of radiographic and scintigraphic techniques to assess aseptic loosening of the acetabular component in a total hip replacement. J Bone Joint Surg Am. 2004;86(11):2456-2463.

22. Moore MS, McAuley JP, Young AM, Engh CA Sr. Radiographic signs of osseointegration in porous-coated acetabular components. Clin Orthop Relat Res. 2006;(444):176-183.

23. Mehin R, Yuan X, Haydon C, et al. Retroacetabular osteolysis: when to operate? Clin Orthop Relat Res. 2004;(428):247-255.

24. Mallory TH, Lombardi AV Jr, Fada RA, Adams JB, Kefauver CA, Eberle RW. Noncemented acetabular component removal in the presence of osteolysis: the affirmative. Clin Orthop Relat Res. 2000;(381):120-128.

25. Beaulé PE, Le Duff MJ, Dorey FJ, Amstutz HC. Fate of cementless acetabular components retained during revision total hip arthroplasty. J Bone Joint Surg Am. 2003;85(12):2288-2293.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.