Use of bone compaction in total knee arthroplasty.

This study compared the effects of bone preparation on tibial stem stability in total knee arthroplasty. Six pairs of fresh-frozen tibias underwent implantation of an 18 x 75-mm press-fit stem (minus the tibial tray). The standard press-fit technique was performed creating a cavity 17 mm in diameter. For the bone compaction technique, stainless-steel dilators were machined ranging in diameter from 6 to 16 mm in 2-mm increments. The technique consisted of using the dilators and a mallet to create a compacted tunnel in a sequential manner to 16 mm in diameter followed by implantation of the stem. The specimens were mounted on a materials testing machine and loads were applied in both planes: anteroposterior and mediolateral. A preconditioning load of 100 N was applied followed by a second 100-N load from which the stiffness (N/mm) of implantation was calculated. The stability of the tibial stems implanted by compaction averaged 84.7% greater when compared with the press-fit stems (P < .017 by multivariate analysis).

Intramedullary versus extramedullary tibial alignment systems in total knee arthroplasty.

One hundred twenty consecutive total knee arthroplasties were performed to compare the accuracy of intramedullary versus extramedullary tibial resection guides. An intramedullary guide (group 1) was used in 60 cases and an extramedullary guide (group 2) was used in another 60 cases. In group 2, the distal portion of the extramedullary guide was shifted 3 mm medial to the midpoint of the ankle in order to position it over the center of the talus. Postoperative tibial component alignment angles were similar in both groups (group 1, 0.43 degrees varus; group 2, 0.36 degrees valgus). However, 88% of tibial components in group 2 were aligned within 2 degrees of the 90 degrees goal versus only 72% of tibial components in group 1. Satisfactory alignment can be obtained with either intramedullary or extramedullary resection guides, although a wider range of error was encountered with intramedullary guide use. Distal positioning of the extramedullary guide over the center of the talus rather than the midpoint of the ankle is important to avoid varus tibial resection. Extramedullary guides avoid the potential complications of intramedullary guide use, including fat embolization and hypoxia, intraoperative fracture, loss of polymethyl methacrylate pressurization, and inability of intramedullary rod passage due to deformity, retained hardware, or pathologic bone disease.

Retained distal femoral osteophyte. An infrequent cause of postoperative pain following total knee arthroplasty.

Persistent postoperative pain following total knee arthroplasty is infrequent. This case report describes an unusual cause of pain, crepitus, and effusion following total knee arthroplasty due to a retained distal femoral osteophyte. Osteophyte removal resulted in total alleviation of this patient's discomfort and swelling.