Uncemented custom femoral components in hip arthroplasty

Abstract

Background and purposeWe have developed an individually designed, uncemented femoral component for achievement of improved strain distribution and fixation to the bone, to make uncemented stems more applicable in femurs of abnormal size and shape, and to improve the joint mechanics. Here we describe the design of the implant and present the results of a prospective clinical study with at least 7 years of follow-up.Patients and methodsThe prostheses are produced by CAD-CAM technique. The design of the stem is based on CT information, and the neck design is based on the surgeon's planning of the center of rotation, femoral head offset, and leg length correction. The first-generation stem produced before 2001 had a proximal HA coating and a sand-blasted distal part that was down-scaled to avoid contact with compact bone. The second-generation stem had a porous coating beneath the HA layer and the distal part of the stem was polished.The implant was used in 762 hips (614 patients) from 1995 until 2009. 191 of these hips were followed for 7 years and 83 others were followed for 10 years, and these hips are included in the present study. Mean age at surgery was 48 (20–65) years. Congenital dysplasia of the hip was the reason for osteoarthritis in 46% and 57% of the hips in respective groups. Merle d'Aubigné score was recorded in 152 and 75 hips in the two groups. Prostheses followed for 10 years, and almost all in the 7-year group, were first-generation stems.ResultsThe 7- and 10-year cumulative revision rates were 1.1% and 2.4%, respectively, with stem revision for any reason as endpoint. The clinical results were similar at 7 and 10 years, with Merle d'Aubigné scores of 17. Intraoperative trochanteric fissures occurred in 2 of the 191 operations (1.0%); both healed after wiring. In hips followed for 7 years, 2 periprosthetic fractures occurred; exchange of the stem was necessary in both. One additional fracture occurred between 7 and 10 years, and it was treated successfully with osteosynthesis. The rate of dislocation was 1.6% and 2.4%, respectively. There was no radiographic loosening at follow-up.InterpretationUse of a custom femoral stem gives a reliable fixation and promising medium-term clinical results in femurs of normal and abnormal shape and dimension. The individual design, which enables optimized joint mechanics, gives a low risk of mechanical complications.

Treatment of Trochanteric Fractures with the Gamma3 Nail - Methodology and Early Results of a Prospective Consecutive Monitored Clinical Case Series

“…The MDA score is a clinician-based mobility score, which consists of two parts: the first part asks two questions about current pain and functional status of the patient, with six possible answers each; the second part consists of arrange of motion (ROM) assessment. The MDA score is frequently used in the assessment of patients after hip fracture [ 10 - 14 ].…”

Custom-Made Femoral Implants in Total HIP Arthroplasty Due to Congenital Disease of the HIP: A Review

“…Variations of the standard “fill and fit” approach have also been reported. Benum et al (19) used slightly oversized stems in initial designs and the technique involved the removal of compact bone. However, in the same centre, the diameter of later custom-made femoral stems was reduced in order to avoid distal diaphyseal fixation.…”

“…The coating is hydroxyapatite with a variety of covering surfaces. In the majority of custom-made femoral stems the hydroxyapatite coating is applied to the proximal part of the implant (12, 19, 20), while Flecher et al (21) used a fully hydroxyapatite coated stem. The thickness of the hydroxyapatite layer varies between 50 and 150 μm.…”

“…Femoral anteversion is, as a rule, provided by the stem according to preoperative measurements, and stem insertion has to follow the native anatomy of the proximal femur. The prosthesis is designed with a neck that gives a femoral neck anteversion of either 10° (19) or 15° (12, 21) after insertion unless the surgeon decides otherwise. However, in cases of excessive femoral anteversion (>45°), it might be more biomechanically sound to perform a derotational osteotomy, either in the subtrochanteric region or distally as in cases with CDH where a standard femoral component is used (23).…”

“…The pertinent literature was published from 2006 to 2015, with a mean follow up ranging from 6 up to 14 years and overall survival rates from 93% to 100% (11, 12, 19–20–21, 32, 33). Moreover, all studies showed statistically significant improvement in postoperative clinical scores (mainly Harris Hip Score and Merle d'Aubigne Score) compared to the preoperative period and the improvement was retained over time.…”