The Journal of Arthroplasty Vol. 11 No. 8 1996 Brief Communication Early Delamination of a Hylamer-M Tibial Insert Michael D. Ries, MD, Anuj Bellare, PhD, Brian J. Livingston, BA, Robert E. Cohen, PhD, and Myron Spector, PhD Recent reports of increased wear rates associ- ated with use of the Hylamer form of ultrahigh- molecular-weight polyethylene (UHMWPE) in total hip arthroplasty have raised concerns about the durability of this material [1,2]. As contact stresses are higher in the knee than the hip, failure of this material may occur more rapidly in total knee compared with total hip arthroplasty despite use of a lower modulus form of Hylamer, Hylamer- M. We have observed delamination wear and gross pitting of a Hylamer-M tibial insert after 2.5 years of clinical use, which indicates that early fatigue wear failure of this modified form of UHMWPE can occur in total knee arthroplasty (TKA). Case Report A 55-year-old woman underwent staged bilat- eral cemented AMK (Depuy, Warsaw, IN) TKA for gonarthrosis. She achieved 120 ° motion and pain relief on the left side, but presented with vague pain, a low-grade effusion, and a range of motion of from 5 ° to 100 ° 2 years after right TKA. Both knees were stable to varus-valgus stress and had mild anteroposterior laxity. Radiographs From The Mary Imogene Bassett Hospital, Cooperstown, New York; Brigham and Women's Hospital, Boston, Massachusetts; and Mas- sachusetts Institute of Technology, Cambridge, Massachusetts. Supported, in part, by the Veterans Administration Rehabili- tation Research and Development Service. Reprint requests: Michael D. Ries, MD, The Mary Imogene Bassett Hospital, Cooperstown, NY 13326. demonstrated good alignment and fixation of the components with no osteolysis or obvious evi- dence of polyethylene wear. Aspiration of the right knee joint fluid was culture negative. Her symp- toms persisted despite treatment with physical therapy and nonsteroidal anti-inflammatory medi- cations. The patient remained dissatisfied with the result of her right TKA, and surgical intervention was offered to obtain biopsy material for possible occult infection, explore the extensor mechanism, and release the posterior cruciate ligament to increase flexion. At operation, the components were found to be well fixed. A yellowish discolored, 10-mm Hylamer tibial insert was identified with delamination wear in both the medial and lateral tibiofemoral com- partments. Flakes of polyethylene debris, measur- ing up to 5 mm, were found in the medial and lat- eral posterior compartments. The posterior capsule was debrided, and the Hylamer insert exchanged for a non-gamma-irradiated conventional UHMWPE insert of the same thickness. The tibial insert displayed pits (> 3 mm in diame- ter and > 1.5 mm deep) and areas of delamination (approximately 1 cm in diameter) in both com- partments (Fig. 1). The insert was analyzed by small-angle x-ray scattering to evaluate crystallite size and the distance separating crystallites, differ- ential scanning calorimetry to determine percent- age crystallinity, and low-voltage, high-resolution scanning electron microscopy to assess the mor- phology in the bulk and at the wear surface. Differential scanning calorimetry of the interior of the nonarticulating portion of the insert 974