Neutral Mechanical Alignment Alters the Native Distal Femoral Joint Line: A Virtual Three-Dimensional Planning Total Knee Arthroplasty Study.

BACKGROUND: Alternative alignment concepts have garnered great interest in an effort to improve patient satisfaction following primary total knee arthroplasty (TKA). The purpose of this study is to determine variation or deviation from an individual's native joint line in primary TKA using neutral mechanical versus a restricted kinematic technique. METHODS: An institutional review board-approved prospective cohort study was performed evaluating the effect of neutral mechanical alignment (nMA) versus a restricted kinematic alignment (rKA) on the native joint line in 100 consecutive patients undergoing primary TKA. Using preoperative computed tomography and intraoperative 3-dimensional software, 2 virtual preoperative plans were created: nMA and rKA. Templated bone resections were recorded. Change in joint line was calculated using known implant planar thickness and planned bone resection. RESULTS: nMA yielded significantly greater deviation from the patient's native joint line along the lateral compartment of the knee (lateral distal femoral condyle, lateral posterior femoral condyle, lateral tibial resection). With nMA, the lateral distal femoral joint line was distalized by a mean 4.3 versus 2.6 mm using rKA technique (P < .001). In rKA, >60% of knees had <3 mm of deviation from the native lateral posterior femoral offset, whereas in nMA, >95% of knees had ≥3 mm change in the lateral posterior femoral condylar offset. CONCLUSION: nMA-TKA resulted in statistically larger joint line deviations compared to rKA-TKA, most notably along the lateral distal femoral condyle joint line. Further analysis is needed to determine the clinical consequences of joint line deviation from the native anatomy using nMA as the target for primary TKA.

No difference in PROMs between robotic-assisted CR versus PS total knee arthroplasty: a preliminary study.

The purpose of this study was to determine if significant clinical differences exist in patient-reported outcome measures (PROMs) between PS and CR TKAs implanted using robotic-assisted technology. This was an IRB-approved retrospective study from an institutional database evaluating 214 knees in 190 patients. Inclusion criteria included: primary RA-TKA, age 22-89 at the time of surgery, preoperative coronal limb deformity within 15º of neutral alignment, and minimum 1-year follow-up. The PS cohort consisted of 103 patients with 107 RA-TKAs, whereas the CR cohort consisted of 87 patients with 107 RA-TKAs. Cohorts were compared on the basis of demographics and PROMs (KSS knee, KSS function, FJS-12, KOOS-JR, WOMAC, and 5-point satisfaction Likert scale) collected preoperatively and at 1-year follow-up. Statistical analyses comparing measures were conducted via Student's t tests for continuous data and Chi-squared analyses for categorical data. There were no significant differences identified in short-term PROMs at 1-year follow-up between cohorts (all p values > 0.05). 93.1% of patients with CR knees and 94.7% of patients with PS knees reported a satisfaction level of "very satisfied" or "satisfied". Revision arthroplasty occurred in six knees (2.8%, 3 knees in CR cohort, 3 knees in PS cohort) with no differences in overall complications between groups. The use of RA-TKA technology promoted high patient satisfaction scores within this study, independent of CR or PS implant type with no significant differences in PROMs, satisfaction, revisions, or complications between the two groups.