The present study showed that the ALA might be superior to the PLA in controlling the short-term postoperative LLD among some of the unilateral primary THA patients. However, their postoperative FO, GO restoration, and LOS are comparable. Both approaches achieved satisfactory joint function within the 20-month follow-up.
Our most import finding is that the ALA might be superior to the PLA in controlling postoperative LLD. The univariate analyses revealed the postoperative LLD were significantly lower and more stable in the ALA group than in the PLA group over 20 months postoperatively. Similarly, multivariate liner regression analysis also revealed that THA approach is significantly associated with postoperative LLD. Notable relationships between discrepancy and approaches were reflected with a higher discrepancy in the PLA group (p = 0.001; β = 4.71; 95% CI, 1.78 to 7.64). These results are highly consistent with several earlier studies . A previous study demonstrated that the accurate reconstruction of biomechanical parameters related to the limb discrepancy after THAs is critical to ensure a long-term success . Nevertheless, discrepancies after THAs may necessitate subsequent interventions but current methods during the operation are either inaccurate or expensive . Intelligent HIP smart tool, a newly introduced smart tool providing an accurate and real-time intraoperative leg length measurements, is properly useful for an improved measurements . Special-designed prostheses , surgeon-controlled table, and advanced fluoroscopic imaging techniques . would improve the biomechanical and physiological hip reconstruction and subsequently enhance the radiographic and clinical outcomes.
Interestingly, both the ALA and PLA are comparable in restoring the postoperative offset. Previous literatures evidenced that the offset parameters (FO, AO, and GO) have significant impacts on the postoperative function rehabilitation and preoperative templating, and the proper intraoperative verification is helpful to achieve an accurate offset restoration, yielding a better abductor strength as well as a long-term successful prognosis [25, 26]. Our data showed that postoperative AO, FO and GO was lower in the ALA group than that in the PLA group. These results indicate that both the ALA and the PLA are possibly proper for the unilateral primary THA in selected conditions regarding the offset restoration in line with the general investigations .
The DDH represents abnormalities of both acetabulum and femur, requiring special techniques to reconstruct its physiological biomechanical [27, 28]. Our data with 81 DDH patients (including 49 young females) showed that the DDH patients tend to yield the more postoperative discrepancy and the DDH diagnosis is a significant contributor to the postoperative LLD. Previous literatures demonstrated that the discrepancy and offset might result from an improper position of the femoral stem and acetabular cup, and special thinner, therefore, shorter stems with more non-sprouted sleeves might be more suitable [29, 30]. Arthroplasty surgeons are recommend paying more attention to the perioperative plan in consideration of high risk of postoperative LLD. External obturator footprint, robotic-assisted intervention, gait training, and 3D-printed individual templates provide personal plan to improve the THA outcomes for DDH patients .
Moreover, the ALA seems cause the less soft tissue damage than the PLA group for the primary THAs with the comparable safety and efficacy. Previous research showed that the joint degeneration is associated with the body weight of patients [32, 33]. However, our data revealed that BMI is not a significant contributor to LLD (p = 0.126; β = 0.30, 95% CI, -0.08 mm to 0.67 mm) but an increased postoperative discrepancy is noticed in patients with a higher BMI (Figure. 3). Therefore, controlling weight might still be helpful for obese patients before the elective surgeries. More studies are necessary to identify such a possible beneficial effect of the body weight controlling strategy for the ultimate success of THAs.
Several limitations should be noticed in this study. First, the retrospective nature of the study might not allow us to draw conclusive statements. Second, significant intergroup difference of patient age was observed with divergent sample size, which seems as an unbalanced group (PLA = 200 vs ALA = 66) of patients with what appears to be predominantly DDH (81/266, ALA = 22, PLA = 59). Third, the follow-up is relatively short, more trails with high-level evidence were needed to confirm the findings from the represent study. Strengths of this study include the detailed comparison and analysis of radiographic data performed in a standard manner with a relatively large and homogenous patients operated by the identical highly experienced surgeon team from a single institution.