Abstract
Introduction: Conventional approaches to cementless revision THR include cemented and cementless stems, which are graft dependent for initial stability (Type 3 reconstructions), distally fixed extensively porous coated implants and modular implants. CT and radiographic visualization, preoperative planning, and patient specific implant fabrication enable the surgeon to achieve the following objectives simultaneously and without compromise: bypass or fill specific bony defects, implement precisely the surgeon’s individual implant design goals, optimise proximal, distal, or regional fit objectives, achieve supplemental fixation via collars, fluted stems, and targeted ingrowth zones/ treatments, and establish head center, neck length, lateral offset, anteversion angle, and leg length.
Methods: This series of cementless titanium implants achieved initial press-fit fixation on host bone with bony attachment via proximally HA coated macrotextured surface. The extramedullary portion of the implant is designed to restore leg length and normal joint mechanics. The initial 44 consecutive revision hips using this rationale were reviewed for inclusion. At surgery, all femoral reconstructions were completed without resorting to Type 3 structural grafts. Six patients died prior to 10 years f/u, and three (4 hips) were lost. Two stems were removed prior to minimum follow up: one at five weeks post-op for deep sepsis, and one for aseptic loosening presumed secondary to metabolic derangements from poorly controlled end-stage renal disease. The remaining 31 patients (34 hips), 18 females and 13 males with a mean age of 61 (range 31-75) and average weight of 168 (85-240) pounds, were evaluated at minimum 10 years (range 10 to 11 years).
Results: All 34 components remain well-fixed (Engh Class 1) at last follow up (97% implant survival). Stress shielding was uncommon outside the calcar region. Average modified Harris Hip Scores were 49 (10-88) pre-operative and 81 (48-100) at final follow-up, with pain scores of 18 (0-44) and 41 (30-44) respectively. Complications included fracture (intraop: 4 fissures, 2 stable type II, 1 unstable type III, and 1 late periprosthetic fractures distally), and three dislocations.
Discussion: The concept of a metaphysical loading, proximally ingrown, collared patient specific revision implant gave results comparable to Engh’s series of extensively coated revision stems, while avoiding the high failure rate associated with structural allograft, the worrisome proximal bone loss associated with fully porous coated stems, the high cost of modular implants.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
