TIP OF STEM PAIN IN REVISION TOTAL KNEE ARTHROPLASTY: A RETROSPECTIVE COHORT STUDY

Tip of stem pain is a challenging complication of revision knee arthroplasty resulting in decreased patient satisfaction. The exact etiology of tip of stem pain is unknown. This study evaluates the incidence of tip of stem pain, as well as the clinical and radiographic outcomes associated with tip of stem pain in revision knee arthroplasty. A total of 974 patients who underwent revision total knee arthroplasty between January 2002 and January 2022 were identified for our retrospective review. Tibia length, femur length, width of tibial isthmus, width of femoral isthmus, and distance from tip of stem to isthmus were collected and compared between patients with and without stem pain. One-way ANOVA, Mann-Whitney U tests, and Fisher Exact tests were used to evaluate association between radiographic outcomes and tip of stem pain. In our study, 974 patients were included, among these cases, 404/974 (41.5%) were men, mean age at surgery was 67.1 years (SD 9.6), and mean BMI was 33.7 kg/m2 (SD 7.7). Of the 974 patients reviewed 24/910 (2.6%) presented with tibial stem pain, and 5/908 (0.6%) presented with femoral stem pain. The mean distance between the tip of stem and tibial isthmus was significantly shorter in patients with stem pain, 3.753 cm (SD 2.467), compared to those without stem pain, 5.608 cm (SD 3.064) (p = 0.0041). There was a significant association between tibial stem length and stem pain, as 24/24 (100%) patients with stem pain had a stem length of 100mm or more (p = 0.0183). There was also a significant difference in the mean femoral length between patients with stem pain, 38.79 cm (SD 0.8429), and those without stem pain, 42.78 cm (SD 3.221) (p = 0.0137). There was no significant difference in tibial length, tibial width, femoral width, femoral stem length, or distance from tip of stem to femoral isthmus between patients with or without stem pain. There was no significant difference in the use of cemented versus uncemented stems, or the type of knee construct used for patients with or without stem pain. Revision total knee arthroplasty is a reliable procedure that has a low incidence of tip of stem pain. Some radiographic variables may play a role in producing stem pain.