J Orthop Sci (2008) 13:433–437DOI 10.1007/s00776-008-1258-y

Original article

Arthroscopy for evaluation of polyethylene wear after total knee arthroplasty

MAKOTO KONDO1, TADASHI FUJII

1, HIROSHI KITAGAWA1, HIROSHI TSUMURA

2, and YOSHINORI KADOYA3

1 Department of Orthopaedic Surgery, Kashiba Asahigaoka Hospital, 839 Kaminaka, Kashiba, Nara 639-0265, Japan2 Department of Orthopaedic Surgery, Medical Faculty, Oita University, Oita, Japan3 Department of Orthopaedic Surgery, Osaka Rosai Hospital, Osaka, Japan

AbstractBackground. The purpose of this report is to demonstrate the severity of polyethylene wear by arthroscopy after total knee arthroplasty (TKA).Methods. Polyethylene wear of TKA prostheses was evalu-ated endoscopically in eight knees (six patients). Arthroscopy was indicated when the patients had persistent but slight hydroarthrosis and instability confi rmed by stress radiogra-phy, but these fi ndings were insuffi cient for a consensus on polyethylene revision. The average interval between primary TKA and arthroscopy was 9 years 3 months.Results. All knees had unexpectedly widespread, severe polyethylene wear characterized by delamination. Based on arthroscopic visualization of the damage to the polyethylene, all patients consented to undergo isolated polyethylene surface revision surgery. The severity of polyethylene wear was worse than anticipated at the evaluation arthroscopy. After a mean follow-up of 5 years 6 months, all knees were stable and symptom-free.Conclusions. The usefulness of arthroscopy is validated in certain groups of patients with polyethylene wear when diagnosed with careful clinical examination and stress radiography.

Introduction

Excellent long-term outcome of total knee arthroplasty (TKA) has been made possible with improved surgical technique and implant design. However, designs of articulating surface or polyethylene material lead to progressive polyethylene wear, resulting in implant damage or loosening. Although polyethylene wear is often progressive, it remains asymptomatic in many cases, with hydroarthrosis and mild instability some-times the only clinical signs indicating wear.1,2 Recurrent

synovitis or repetitive stretching of ligaments in daily living may lead to hydroarthrosis and instability. If these symptoms are faint and trivial despite a suspicion of polyethylene wear and component damage, both the surgeon and patients hesitate to undertake revision surgery. It is clinically important to devise a strategy that can diagnose polyethylene wear accurately. To evaluate polyethylene wear under direct vision, we employed arthroscopy in post-TKA knees1,3–5 and dem-onstrated mild chronic effusion and instability by stress radiography long after TKA. The method and effi cacy of arthroscopy in these knees are reported.

Subjects and method

Eight knees of six patients with satisfactory outcomes following TKA but later presenting with hydroarthrosis and instability underwent arthroscopy for an accurate evaluation of polyethylene wear of the TKA prosthesis (polyethylene surface). TKA was performed in three knees of three patients for osteoarthritis (OA) and in fi ve knees of three patients for rheumatoid arthritis (RA). The average age of patients at the time of TKA was 60.2 years (53–65 years). Three knees underwent MG-I TKA, four knees Genesis CR TKA, and one knee Genesis PS TKA. The average interval between primary TKA and arthroscopy was 9 years 3 months (6 years 1 month to 11 years 5 months).

The degree of lateral instability on the coronal plane was evaluated by the angle formed between the femoral and tibial components as indicated by stress radiogra-phy. Varus instability was 6.7° ± 2.8° (2.5°–9.9°), and valgus instability was 2.9° ± 2.3° (0.1°–5.6°). Although varus instability at arthroscopy was signifi cantly more severe (paired t-test) than at 3 years 2 months after arthroplasty, it did not confi rm polyethylene wear, which meant, therefore, that we were unable to reach a defi nitive diagnosis of polyethylene wear. A feeling of

Offprint requests to: T. FujiiReceived: January 21, 2008 / Accepted: June 2, 2008

434 M. Kondo et al.: Polyethylene wear after TKA

instability while stair ascending/descending with moder-ate hydroarthrosis was the only complaint.

The purpose and importance of arthroscopy were dis-cussed with the patients, and consent was obtained from all six patients before arthroscopy. The average thick-ness of the original polyethylene surface was 10.4 mm (range 8.0–13.5 mm), and the surfaces were all rela-tively fl at in design, including the PS insert (Table 1). The paired t-test was employed for all statistical analyses.

Arthroscopy

Two arthroscopes were used after careful consideration of the sequence of insertions to avoid causing damage to the components. A tourniquet is strongly recom-mended because bleeding is an obstacle to accurate orientation, and blind manipulation may damage the surface of the components.

The fi rst portal was created at a lateral suprapatellar region to secure the visual fi eld in the joint. This portal

is a safe distance from damaging all components. Using a sharp-pointed triangular scalpel, and taking precau-tion not to contact or damage the components visual-ized with the fi rst scope, a lateral infrapatellar portal was created (Fig. 1a), where the second scope was inserted (Fig. 1b). After removing the fi rst scope at this point, the second scope was used for observation (Fig. 1c). The lower limb hung free, and the knee was fl exed as necessary to visualize the entire polyethylene surface.

Case report

A 75-year-old woman (case 4) had undergone TKA for OA and received a Genesis CR implant with a 12-mm polyethylene surface when she was 63 years old. Her postoperative outcome was excellent, and she was able to squat without support. Stress radiography performed 2 years 5 months postoperatively demonstrated the knee to be stable (Fig. 2a). She remained asymptomatic; but because of mild hydroarthrosis, stress radiography

Table 1. Details of cases

Case no.

Age at TKA (years) Sex Disease R/L

Type of TKA

Thickness of polyethylene (mm) Interval from

TKA to arthroscopy

F/U after revisionPrimary Revision

1 56 F RA R MG I 13.5 13.5 10Y 11M 6Y 3ML MG I 8.5 11 9Y 3M 7Y 9M

2 64 F RA R MG I 11 20 8Y 7M 7Y 5M3 53 F RA R Genesis CR 10 15 10Y 3M 4Y 8M

L Genesis CR 8 12 10Y 2M 4Y 8M4 63 F OA L Genesis CR 12 15 11Y 5M 3Y 4M5 65 F OA R Genesis PS 8 10 6Y 1M 6Y 10M6 60 M OA R Genesis CR 12 12 8Y 5M 3Y 5MAverage 60.2 10.4 13.6 9Y 3M 5Y 6M

TKA, total knee replacement; R/L, right/left; F/U, follow-up; RA, rheumatoid arthritis; OA, osteoarthritis; Y, years; M, months

Fig. 1. Arthroscopic technique. a A lateral suprapatellar portal is created (arrow 1) to observe the lateral subpatellar region. Being careful not to damage the components, a sharply pointed triangular scalpel is used to create a lateral subpatel-lar portal (arrow 2). b Under direct view from the fi rst portal,

the second scope is inserted while being careful not to contact or damage the components (arrow). c The polyethylene is evaluated under direct view of the scope inserted through the lateral subpatellar portal (arrow) while the knee hangs free and is fl exed as necessary to examine the entire component

M. Kondo et al.: Polyethylene wear after TKA 435

was again performed 11 years 5 months postoperatively, which confi rmed instability (Fig. 2b). Further question-ing revealed that she was suffering only mild discom-fort, and stair ascending/descending was not as smooth as it used to be. After obtaining her consent, arthros-copy confi rmed delamination of the polyethylene surface over a large area; more specifi cally, delamina-tion had occurred on the entire weight-bearing region on the medial side, mainly anteromedially, where the weight was especially applied through the medial condyle (Fig. 3b) on the intercondylar region (Fig. 3c). Delamination had mainly occurred at a posterior site on the lateral side (Fig. 3d) as well. The severity and the area of retrieved polyethylene wear were greater than

we had anticipated with stress radiography (Fig. 3a). Both femoral and tibial components presented fi rm fi x-ation to each bone. Revision consisted of isolated poly-ethylene exchange from 12 mm to 15 mm of the surface, as neither component was damaged. The knee became stable after revision surgery (Fig. 2c), and the patient showed no further problem for 3 years 4 months.

Results

Using the method described above, arthroscopy was successfully conducted in all knees without causing any damage to the components, and polyethylene delamina-

Fig. 2. Instability is noted with time (stress radiography). a The knee is stable at 2 years 5 months after total knee arthro-plasty (TKA). b Stress radiography performed 11 years 5

months after TKA shows medial instability of 8.8° and lateral instability of 4.1°. c Polyethylene exchange from 12 mm to 15 mm, resulting in stability

Fig. 3. Arthroscopic fi ndings and wear characteristics of the retrieved polyethyl-ene. a Retrieved polyethylene. b Wear characteristics of the medial region. c Wear characteristics under the intercon-dylar space. d Wear characteristics of the lateral region

436 M. Kondo et al.: Polyethylene wear after TKA

tion was confi rmed in all subjects. Arthroscopic fi ndings proved to be extremely useful for explaining to patients the degree of polyethylene wear necessitating revision surgery, and all patients consented to undergo revision. Because none of the knees showed loosening between the components and the bone, revision of isolated poly-ethylene surfaces was performed.

A survey of the overall polyethylene surface showed deep erosion and fragmentation in the posterior site. Had these areas been left untreated, the knee might have encountered metallosis in the short term, leading to signifi cant bone loss in the long term. At an average of 5 years 6 months (3 years 4 months to 7 years 9 months) following revision, all knees remain signifi -cantly stable (varus 2.6° ± 0.9°; valgus 1.8° ± 1.2°; paired t-test) and are on track to good outcomes (Table 2). The HSS scores were 89.5 ± 2.3 on average at arthroscopy and 90.4 ± 2.1 at the fi nal follow-up examination.

Discussion

Polyethylene wear is a signifi cant clinical concern affect-ing the long-term outcome of TKA. Delamination of a polyethylene surface leads to mechanical instability and, if left untreated, risks metallosis by metal-with-metal contact. For this reason, immediate and accurate detection of wear by visualization is necessary. However, the evaluation using conventional X-ray photography including stress radiography is diffi cult.6,7 Arthroscopy procedure is a specialized surgical procedure performed by orthopedic surgeons in some countries; and one would hesitate to perform such a procedure because of the additional expense. Total revision surgery involves further cost and surgical skill. These are the most im portant factors responsible for the low rate of total revision.

Arthroscopic examination following TKA risks infec-tion or component damage, and therefore it is not a technique applied routinely and is often avoided. Some studies, however, have reported the use of arthroscopy in post-TKA knees for diagnosing fi broarthrosis3 and patellar clunk syndrome4 or in patients with severe pain of unknown cause.1,5 To our knowledge, this is the fi rst attempt to apply arthroscopy for the detection and eval-uation of less symptomatic polyethylene wear after

TKA. All knees in our series, including the one with a PS implant, had a polyethylene fl at surface. During the same period, knees operated on and implanted with IB-II, a highly constrained design, did not encounter any signifi cant instability or hydroarthrosis. This sug-gests that knees implanted with polyethylene of fl at design need to be closely observed for instability and chronic hydroarthrosis because the severity of wear and tear found in the removed polyethylene was worse than anticipated during arthroscopy. Nevertheless, revision of all the components is a drastic remedy and should be considered only when no other options are available. Patients with long-term TKAs who have few symptoms may also be subjected to unanticipated vast delamina-tion of the polyethylene surface. Our fi ndings strongly support that polyethylene exchange surgery prior to development of any major clinical problems is the key to successful revision.

Compared with regular arthroscopy, the visual fi eld is limited; and the posterior site, which is the area that is most deteriorated, cannot be accurately observed. However, arthroscopy has proven to be advantageous as it allows direct observation of polyethylene’s wear characteristics through relatively minimal invasion. Arthroscopic fi ndings were also helpful in convincing patients of the importance of polyethylene exchange surgery and in obtaining their consent to undergo timely revision surgery.

Recently, numerous articles have addressed polyeth-ylene wear and exchange, and some are reporting knees with instability8 after TKA, implant malalignment,9 or severe pain resulting in a poor outcome with isolated polyethylene exchange.1 In our series, however, poly-ethylene exchange was conducted in all subjects, who experienced no pain and were able to ascend/descend stairs a few days after surgery and have maintained good outcomes lasting on an average of 5 years 6 months after revision, although close follow-up of these patients is still necessary.

We believe that the good outcomes were due to revi-sion being performed at a proper time through minimal invasion. The timing of the arthroscopy is an important factor for revision surgery to be successful. If polyeth-ylene wear is allowed to progress signifi cantly, metal components will come into contact with each other, possibly leading to metallosis, which in turn causes

Table 2. Instability

Instability 3Y2Ma 9Y3M at arthroscopya 14Y8M fi nal follow-upa

* **

Varus (°) 3.5 ± 1.3 6.7 ± 2.8 2.6 ± 0.9Valgus (°) 2.2 ± 1.3 2.9 ± 2.3 1.8 ± 1.2a Mean follow-up period after TKA* P = 0.022; ** P = 0.009

M. Kondo et al.: Polyethylene wear after TKA 437

component damage and eventually signifi cant bone loss. The latter then leads to further unavoidable com-plicated revision surgery. Although the surgical tech-nique for complicated revision cases is gradually being established, polyethylene exchange surgery is simple, only moderately invasive, and hardly traumatic for the patients. It has an additional advantage of being less expensive for the patient as well.

Conclusion

Arthroscopy after TKA is an option for discovering serious polyethylene wear that requires revision surgery even for patients with mild symptoms.

Acknowledgment. The authors thank Drs. Takashi Azuma and Moses Paul and Mss. Eiko Masui, Ikuko Hirao, and Kaori Watanabe for their assistance in preparing this article.

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