Outcomes of total knee arthroplasty in degenerative osteoarthritic knee with genu recurvatum.

Background: This study aimed to assess the incidence of genu recurvatum without neuromuscular disorders in knees that underwent navigation-assisted total knee arthroplasty (TKA), to evaluate short-term radiologic and clinical results of navigation-assisted TKA in genu recurvatum, and to evaluate differences in results according to the degree of pre-operative hyperextension and type of implant and insert.

Methods: This study retrospectively reviewed 510 knees that underwent navigation-assisted TKA from January 2005 to December 2011. The incidence of knees that showed hyperextension of ≥5° (genu recurvatum) on navigation, and the accompanying alignment were evaluated. It assessed radiologic, intraoperative, and clinical results in recurvatum and control groups by using propensity score matching.

Results: A total of 465 knees underwent navigation-assisted TKA for degenerative osteoarthritis. Genu recurvatum was observed in 55 knees (11.8%). Of these, 41 knees (74.5%) had degree of hyperextension between five degrees and 10°, and 47 (85.4%) had varus alignment. The thickness of the resected distal femur in the recurvatum group (7.6±1.6mm) was less than that in the control group (8.4±1.4mm, P=0.001). The thickness of the insert in the recurvatum group (12.5±2.3mm) was greater than in the control group (10.8±1.5mm, P<0.001). The sagittal alignment at the final follow-up was 1.3±3.4° in the control group and -0.1±0.7° in the recurvatum group (P=0.003). Subgroup analyses in the recurvatum group showed no significant difference in sagittal alignment and patient-related outcomes by degree of pre-operative hyperextension and implant/insert type (P>0.05 for all parameters).

Conclusions: Genu recurvatum was not uncommon among patients undergoing primary TKA. This review obtained satisfactory short-term clinical and radiologic results, with a smaller distal femoral resection and thicker insert.