Abstract
Introduction: Patient specific cementless femoral components for THR were developed as a means of addressing the anatomic variations of the proximal femur and hip joint in an effort to achieve long term implant survival and optimum patient function. Design rules were developed with goals of achieving rigid initial stability, maximal endosteal contact for bone integration, and the precise restoration of hip kinematics.
Methods: Beginning in 1989, this series of cementless titanium implants included proximal circumferential HA coating over a macrotextured surface for biologic fixation. All patients who were candidates for cementless arthroplasty (age < 65, active, or overweight) received a custom femoral component. Forty-nine consecutive primary THR in 39 patients were performed during the study period. No patients died and one patient was lost prior to 10 years; all had well fixed stems at latest follow up. The remaining 38 patients (48 hips), 16 females and 22 males, with average age 54 (28-70) and weight 181 (98-270) at surgery, were evaluated at minimum 10 years (range 10-11).
Results: Average modified Harris Hip Scores were 49 (27-87) pre- and 89 (24-100) postoperatively, with pain scores of 17 (0-40) and 42 (10-44) respectively. All femoral components remain well-fixed (Engh Class 1) at final follow-up. No areas of osteolysis were seen distal to the proximal HA-bone interface. Small, focal areas of probable osteolysis were seen at the implant shoulder (4 cases), at the calcar corner (2 cases), and at both sites (1 case). Complications included four proximal margin femoral fissures recognised at surgery, two patients with dislocation, and one non-fatal PE. Reoperations included six head and liner exchanges; two for recurrent dislocation, and four for excessive wear with associated osteolysis (3 pelvic, 1 femoral); and one for fixation and grafting of a trochanteric nonunion.
Discussion: The use of cementless femoral implants based on individual patient characteristics and a set of strict design rules has resulted in excellent clinical and radiographic results at 10-year follow-up. Recent data with some OTS systems have shown comparable excellent results and have diminished the need for the routine use of custom implants in uncomplicated primary situations. However, this series validates the design concepts of this system, supports its use in more complex situations, and suggests applicability on a routine basis where other available implants may be less than optimal.
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.
