Insufficient lateral stem contact is an influencing factor for significant subsidence in cementless short stem total hip arthroplasty.

BACKGROUND: Subsidence is one of the concerning early complications in cementless femoral stem. Few publications have studied the influencing factors for subsidence in short cementless stems, due to their metaphyseal anchoring without diaphyseal invasion, they might demonstrate different subsidence patterns than with the conventional stems. AIM: To analyze the factors associated with significant subsidence in short stems, including any radiographic parameters. METHODS: The digitized radiographs of 274 consecutive short stem total hip arthroplasties were retrospectively reviewed. Subsidence, neck-filling ratio (NFR), seating height and lateral stem contact were evaluated after a minimum of two years follow-up. A threshold of subsidence > 3 mm was considered a clinically significant migration. RESULTS: For the entire cohort, subsidence occurred in 75 cases (27.4%) with the mean stem subsidence of 0.5 mm. (0-12.7, 1.68). Twelve hips (4.4%) had significant subsidence (> 3 mm). The univariate regression analysis demonstrated that age, diagnosis, BMI, Dorr's type B, NFR, and seating height had no significant influence on significant subsidence, whereas insufficient lateral stem contact (≥ 1 mm) did have a statistically significant influence [Odds ratio (OR) = 5.02; 95%CI: 1.3-18.9; P = 0.017]. The multivariate regression analysis also demonstrated that insufficient lateral stem contact was a statistically significant influencing factor (OR = 5.5; 95%CI: 1.4-21.4; P = 0.014). There was no femoral stem revision for aseptic loosening in our cohort. CONCLUSION: This study demonstrated that insufficient lateral stem contact was a statistically significant influencing factor on significant subsidence. Therefore, it is a particularly important step to create proper lateral cortical contact when performing the short stem total hip arthroplasty.

Mid-term results of short-stem total hip arthroplasty in patients with Crowe type I and II developmental dysplasia of the hip.

BACKGROUND: This study aimed to evaluate the clinical and radiographic mid-term results of short-stem THA in patients with DDH. METHODS: We reviewed 32 cases that underwent Metha stem between November 2010 and February 2015. WOMAC scores, Oxford Hip Scores (OHS) and Harris Hip Scores (HHS) were recorded to evaluate the clinical results. The appearance of bone trabeculae development and stress shielding was analyzed. RESULTS: The mean age of patients was 50.3 years (33-67) with the mean follow-up of 77 months (60-106). According to Crowe classification, 13 cases were graded as Crowe I and 19 cases as Crowe II. According to Dorr classification, 17 cases were graded as Dorr A and 15 cases as Dorr B. The postoperative WOMAC scores decreased, and OHS and HHS increased significantly compared with preoperative (p < 0.001). The caput-column-diaphysis angles decreased significantly (p < 0.001) and limb length discrepancy decreased significantly (p = 0.013) after surgery. The radiographic change around the stem showed bone trabeculae development at zones 1 (93.9%), 2 (93.9%), 3 (25%), 5 (6.3%), 6 (96.9%) and 7 (90.6%). There was grade 1 stress shielding in 30 cases (93.9%). There was no stem subsidence greater than 2 mm in all hips, no sciatic nerve injury or no dislocation. Neither acetabulum nor femoral stem was defined as definite loosening, and none of the implants was revised. CONCLUSIONS: The short stem showed promising mid-term clinical results in patients with DDH. The radiographic results demonstrated that the short stem provided physiological proximal load transfer with less stress shielding, being a useful alternative for femoral reconstruction.

Cup Alignment Change after Screw Fixation in Total Hip Arthroplasty.

BACKGROUND: Cup malalignment increase impingement, dislocation, cup migration, and polyethylene wear. Screw fixation for enhanced stability is the preferred option in cases of doubtful primary cup stability. There have been few studies about alignment changes after screw fixation, which may be another cause of cup malalignment. This study aimed to evaluate cup alignment change after screw fixation. MATERIALS AND METHODS: Patients undergoing imageless navigation total hip arthroplasty using screws fixation for acetabular cup were corrected. After the press-fit cup was fully seated, the cup orientation was recorded. After screws were inserted, the cup orientation was recorded again to calculate the alignment change. RESULTS: There were 99 cases with a mean age 63.7 years (25-93). Alignment change after screw fixation was found in 73 cases (73.7%). There were 56 cases (56.6%) with inclination angle change and the mean change was 2.21° (0°-8°). The inclination angle increased in 47 cases (47.5%) with 9 cases (9.1%) increased by 5° or more and decreased in 9 cases (9.1%). There was statistically significant difference between patients using one screw and patients using two or more screws in inclination angle change, 1.56° (0°-5°) and 3.4° (0°-8°), respectively (P = 0.0039). There was statistically significant correlation between inclination angle change and number of screws (r = 0.5401, P < 0.01). There were 49 cases (49.5%) with anteversion angle change and the mean change was 1.67° (0°-5°). The anteversion angle increased in 31 cases (31.3%), decreased in 18 cases (18.2%) with two cases (2%) decreased by 5° or more. There was significant difference between patients using one screw and patients using two or more screws in anteversion angle change, 1.46° (0°-5°) and 2.21° (0°-5°), respectively (P = 0.009). There was significant correlation between anteversion angle change and number of screws (r = 0.284, P = 0.048). CONCLUSIONS: Changes in cup alignment after screw fixation were detected in most cases. It is one possible cause of cup malalignment.