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Limb lengthening common after total knee arthroplasty
study
April 2008
SAN FRANCISCO - Patients typically experience an increase in limb length after
undergoing total knee arthroplasty, according to a study presented here.
In particular, correcting preoperative valgus deformities can lead to larger
increases in limb length vs. preoperative varus deformities, the study authors
noted.
"Patients should be advised preoperatively about the likelihood of limb
lengthening as a consequence of total knee arthroplasty (TKA)," they said in the
study.
Jason E. Lang, MD, and colleagues investigated changes in
limb length occurring after TKA performed in 102 knees of 98 patients. The
investigators obtained full-length standing radiographs using a radiographic
marker, and used the IMPAX digital radiography software (Agfa-Gevaert NV) to
measure limb lengths and the mechanical and anatomic axes.
They displayed their results in a poster at the American Academy of Orthopaedic
Surgeons 75th Annual Meeting.
Preoperatively, coronal alignment averaged 2.48� for the 102 knees overall and
averaged 8.67� among 66 knees with varus alignment and 8.91� among 36 knees with
valgus alignment.
After surgery, coronal alignment improved to average 0.98� overall and averaged
2.9� among preoperative varus knees and 1.06� among the preoperative valgus
knees, according to the study.
Overall, 82 of the 102 knees (80.4%) experienced an increase in limb length
after surgery, including 77% of the varus group and 86% of the valgus group.
The overall increase in limb length averaged 6.3 mm, with a mean increase of
5.17 mm for the varus group (P < .0001) and 8.38 mm for the valgus group (P <
.0001), according to the study.
"This change in limb length results from the restoration of the joint space with
the prosthetic components, as well as from a correction of the coronal and
sagittal deformities commonly seen in patients with knee osteoarthritis," the
authors wrote.
However, no correlation was found between limb lengthening and the type of
prosthesis used � posterior stabilized vs. cruciate-retaining, they noted.
For more information:
Lang JE, Lonner JH, Scott RD, et al. Limb lengthening is a common consequence of
total knee arthroplasty. P163. Presented at American Academy of Orthopaedic
Surgeons 75th Annual Meeting. March 5-9, 2008. San Francisco.
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