Abstract
Four pairs of fresh-frozen cadaver knees (eight knees, four male knees) with a mean age of 72 ± 7 years were used for tests involving a customized simulator capable of controlling quadriceps loading conditions. The muscle force distribution of the quadriceps for the normal loading condition was applied on the basis of muscle cross-sectional area data, as previously reported (VM: 31 N; RF/VI: 49 N; VL: 45 N). To simulate vastus medialis (VM) impairment, we set the muscle force for VM in the muscle force distribution of the quadriceps at zero (VM: 0 N; RF/VI: 49 N; VL: 45 N). The joint reaction forces and moments on knee joints that underwent total knee arthroplasty (TKA) did not differ significantly according to VM impairment status for all flexion angles (p > 0.05). Nevertheless, the vectors of internal–external moments mostly showed a tendency for alteration from external to internal due to VM impairment. This tendency was evident in 9 cases in 12 total test pairs (with and without VM impairment). Furthermore, the vectors of the anterior–posterior reaction forces mostly showed a tendency to increase anteriorly due to VM impairment. This tendency was also evident in 9 cases in 12 total test pairs (with and without VM impairment). These results indicate that posterior dislocation of the tibia may be induced if VM impairment occurs after TKA. In conclusion, VM impairment in knee joints undergoing TKA may contribute to posterior dislocation of the tibia by a paradoxical roll-back with enhancements of the anterior joint reaction force and external moment during knee-joint flexion. Our findings may be valuable for understanding the mechanism of potential instability and malfunction due to VM impairment in knee joints after TKA, and may help to optimize clinical/rehabilitation training plans to improve the prognosis (stability and function) of knee joints undergoing TKA.
Highlights
Total knee arthroplasty (TKA) is an orthopedic surgical approach that is widely applied for patients with severely painful joint diseases, with a high success rate of >90%
The quadriceps were separated into individual components: rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), and vastus medialis (VM)
Forces on quadriceps with/without VM impairment were significantly different at 10°
Summary
Total knee arthroplasty (TKA) is an orthopedic surgical approach that is widely applied for patients with severely painful joint diseases (e.g., degenerative arthritis, inflammatory arthritis, and avascular necrosis), with a high success rate of >90%. TKA survival rates reportedly exceed 95% at 10 years and 90% at 15 years [1,2]. Replacement Registry reported that TKAs were performed for approximately 0.5 million people in the USA in 2016 and will be performed in approximately 3 million people annually worldwide after 2030 [3,4,5]. TKA continues to exhibit failures generally related to pain, infection, osteolysis, wear, aseptic loosening, periprosthetic fracture, instability, or malalignment [5]. Quadriceps impairment is considered the main type of muscle impairment in patients who have undergone TKA [11,12,13,14]
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