Uncemented custom femoral components in hip arthroplasty. A prospective clinical study of 191 hips followed for at least 7 years.
OBJECTIVE
We 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.


METHODS
The 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.


RESULTS
The 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.


CONCLUSIONS
Use 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.
Benum
Pål
P
Department of Orthopaedics, St. Olav's University Hospital, Trondheim, Norway. pal.benum@ntnu.no
Aamodt
Arild
A
D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D005500:Follow-Up Studies; D006618:Hip Dislocation, Congenital / Q000000981:diagnostic imaging / Q000601:surgery; D006622:Hip Prosthesis / Q000009:adverse effects; D006801:Humans; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000601:surgery; D011300:Preoperative Care; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D017755:Prosthesis Fitting; D011859:Radiography; D012086:Reoperation; D016474:Weight-Bearing
Ital J Orthop Traumatol. 1988 Dec;14(4):429-33
3267677
J Bone Joint Surg Br. 2007 Dec;89(12):1574-80
18057355
Clin Orthop Relat Res. 2004 Mar;(420):130-4
15057088
J Comput Assist Tomogr. 1987 Sep-Oct;11(5):804-9
3655042
Hip Int. 2002 Jul - Sep;12(3):263-273
28124316
Clin Orthop Relat Res. 2006 Dec;453:75-80
17016216
Clin Orthop Relat Res. 1989 Dec;(249):73-8
2582679
J Bone Joint Surg Am. 1954 Jun;36-A(3):451-75
13163078
J Bone Joint Surg Br. 1992 Jan;74(1):28-32
1732260
Acta Orthop. 2009 Aug;80(4):420-5
19513891
Clin Orthop Relat Res. 2008 Jul;466(7):1652-6
18470576
Clin Orthop Relat Res. 2006 Sep;450:138-44
16568002
Z Orthop Unfall. 2007 Sep-Oct;145(5):574-8
17939066
J Arthroplasty. 2004 Oct;19(7):837-44
15483798
J Arthroplasty. 1995 Oct;10(5):592-7
9273368
J Bone Joint Surg Br. 1999 Jan;81(1):143-7
10068022
Clin Orthop Relat Res. 1989 Dec;(249):97-112
2582680
J Bone Joint Surg Br. 2000 Nov;82(8):1151-5
11132277
J Bone Joint Surg Am. 2004 Apr;86(4):783-6
15069144
Clin Orthop Relat Res. 2005 Aug;(437):169-75
16056046
J Bone Joint Surg Br. 2001 Aug;83(6):921-9
11521940
Clin Orthop Relat Res. 1989 Dec;(249):79-96
2684468
J Bone Joint Surg Br. 2008 Mar;90(3):299-305
18310749
Int Orthop. 2008 Jun;32(3):317-23
17323091
Int Orthop. 2006 Oct;30(5):375-80
16761147