The ‘critical trochanter angle’ does not show superiority over the CCD angle in predicting varus stem alignment in cementless short-stem total hip arthroplasty

Purpose Varus positioning of the femoral stem can affect the hip offset (HO). The critical trochanter angle (CTA) was introduced in 2019 as a novel geometric angle, to predict varus stem alignment in cementless straight stem THA. The aim of this study was to evaluate the applicability of the CTA as a predictor for stem alignment in THA with a cementless neck resecting short stem. Patients and methods In this retrospective study, 106 patients (index surgery 2014–2019) with unilateral THA and a morphologically healthy contralateral hip as a reference (Kellgren–Lawrence ≤ 1) were included. A cementless short stem with meta-diaphyseal fixation and press-fit cup was implanted in all cases. Stem alignment, CCD angle, CTA and offset reconstruction were measured on preoperative and 3 months postoperative AP radiographs of the pelvis. Results Preoperative lower CTA and lower CCD angle were positively correlated (r = 0.472; p < 0.001). Higher varus stem alignment is correlated with lower CTA (r = − 0.384; p < 0.001) and lower CCD angle (r = − 0.474; p < 0.001). A CTA of 23.1° or lower showed a sensitivity of 59.1% and a specificity of 87.1% (AUC: 0.733) and a CCD angle of 132.75° or lower a sensitivity of 68.2% and a specificity of 80.6% (AUC: 0.77) for a varus stem alignment > 3°. Conclusion The CTA is also applicable in cementless THA with a neck resecting short stem to evaluate risk of intraoperative varus stem positioning. The CCD angle shows higher sensitivity with marginally lower specificity. Therefore, the CTA is not superior in predicting varus stem alignment in short-stem THA. Level of evidence IV.

Hip implants can restore anatomical and medialized rotation centres in most cases

Aims Hip arthroplasty does not always restore normal anatomy. This is due to inaccurate surgery or lack of stem sizes. We evaluated the aptitude of four total hip arthroplasty systems to restore an anatomical and medialized hip rotation centre. Methods Using 3D templating software in 49 CT scans of non-deformed femora, we virtually implanted: 1) small uncemented calcar-guided stems with two offset options (Optimys, Mathys), 2) uncemented straight stems with two offset options (Summit, DePuy Synthes), 3) cemented undersized stems (Exeter philosophy) with three offset options (CPT, ZimmerBiomet), and 4) cemented line-to-line stems (Kerboul philosophy) with proportional offsets (Centris, Mathys). We measured the distance between the templated and the anatomical and 5 mm medialized hip rotation centre. Results Both rotation centres could be restored within 5 mm in 94% and 92% of cases, respectively. The cemented undersized stem performed best, combining freedom of stem positioning and a large offset range. The uncemented straight stem performed well because of its large and well-chosen offset range, and despite the need for cortical bone contact limiting stem positioning. The cemented line-to-line stem performed less well due to a small range of sizes and offsets. The uncemented calcar-guided stem performed worst, despite 24 sizes and a large and well-chosen offset range. This was attributed to the calcar curvature restricting the stem insertion depth along the femoral axis. Conclusion In the majority of non-deformed femora, leg length, offset, and anteversion can be restored accurately with non-modular stems during 3D templating. Failure to restore hip biomechanics is mostly due to surgical inaccuracy. Small calcar guided stems offer no advantage to restore hip biomechanics compared to more traditional designs. Cite this article: Bone Jt Open 2021;2(7):476–485.

Digital templating for the implantation of a curved short hip stem with an anterolateral MIS approach shows gender differences in digital templating

Purpose Digital templating shows reliable accuracy for straight stem systems. In recent years, the implantation of short stems through minimally invasive approaches has gained more popularity. Minimally invasive approaches (MIS) show the risk of undersizing femoral components. Therefore, we questioned the planning adherence for a curved short stem and a bi-hemispherical acetabular cup implanted through an anterolateral MIS approach. Methods A consecutive series of 964 hips (index surgery between 2014 and 2019) with Fitmore® curved short stem and Allofit/-S® acetabular cup (both ZimmerBiomet Inc, Warsaw, IN) were included. Preoperative digital templating was conducted anterior–posterior (AP) digital radiographs of the hip using mediCAD® version 5.1 (Hectec GmbH, Altdorf, Germany). The templates of acetabular and femoral components (offset option and stem size) were retrospectively evaluated for general adherence, and according to sex, BMI and planner’s experience. Results Planning adherence for the exact offset option was 70.6 and 21.6% for exact offset option and stem size. Adherence for acetabular cup ± 1 size was 74.8%. A significant difference between male and female patients for the offset option could be found (p = 0.03, z = −2983). In 22.5% of male patients, an offset option one size higher and in 12.3% of female patients an offset option one size smaller than templated was used intraoperatively Conclusion Digital templating for the Fitmore® stem in cementless THA with a minimally invasive anterolateral approach shows comparable planning adherence to the existing literature for this cementless short stem. However, a lower planning adherence was detected compared to conventional straight stem systems. In male patients, the femoral offset is frequently undersized and in female patients frequently oversized compared to the preoperative plan. Surgeons should be aware of this difficulty in digital templating for Fitmore® hip stem.

Abductor Muscle Force after Straight-Stem Compared to Short-Stem Total Hip Arthroplasty through a Modified Direct Lateral Approach: Functional Assessment of 70 Consecutive Patients of a Randomized Controlled Clinical Trial

Because of preservation of proximal femoral bone stock and minimized soft tissue trauma, short-stem implants are becoming increasingly important in total hip arthroplasty (THA). The postulated advantage regarding the functional outcome has not been verified. We hypothesized an increased abductor muscle strength by the use of a short-stem design. Seventy consecutive patients of a randomized clinical trial were included. Of these, 67 patients met the inclusion criteria after 12 months. Thirty-five patients received a standard straight stem and 32 patients a short-stem femoral component. All surgeries were performed by a modified direct lateral approach. Isometric muscle strength of the hip abductors was evaluated preoperatively 3 and 12 months after surgery. Harris hip score (HHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were evaluated. After three months, there were no differences between the two groups; the abductor force was comparable to the preoperative initial values. After 12 months, a significant increase in muscle strength for the short stem patient group compared to preoperative baseline values was measured (straight-stem THA, 0.09 Nm/kg ± 0.4, p = 0.32; short-stem THA, 0.2 Nm/kg ± 0.3, p = 0.004). Comparison of the 12-month postoperative total HHS and WOMAC revealed no significant differences between both groups. A significant increase in hip abductor muscle strength 12 months after short-stem THA compared to conventional-stem THA was observed.

Short-stem total hip arthroplasty is not associated with an earlier return to work compared to a straight-stem design

Return to work (RTW) has been specifically identified as a high priority in patients undergoing total hip arthroplasty (THA). This investigation sought to assess the effect of the stem design on patients’ RTW. Secondly, the study aimed to identify risk factors that lead to a delayed RTW. Questionnaires inquiring about RTW, employment history, educational level, type of work, physical demands and joint awareness were administered by post. Further data were collected from patients’ hospital records. 176 patients who underwent THA using a short-stem and 97 patients using a straight-stem design were compared. The median return to work time was 10 weeks [IQR 7–14 weeks], with no significant difference between the two groups (short stems vs. straight stems; 10 [IQR 7–14] vs. 11 [7.5–13.5] weeks; p = 0.693). In the multivariate linear regression analysis, self-employment vs. employee (p = 0.001), dimension of preoperative workload (p = 0.001), preoperative sick leave (p < 0.001), and hospital length of stay (LOS) (p < 0.001) independently affected the period until work was resumed. The Forgotten-Joint-Score-12 showed no significant difference between the two groups. The data show that the majority of THA patients can expect to resume work and stem design has no impact on RTW. Employees with preoperative sick leave, prolonged hospital LOS and low workload are at higher risk for a delayed RTW.

Straight stem and threaded cup in patients under 60 years of age: 28.8–30.2 years of follow-up

Purpose The aim of this retrospective observational study of one cohort was to evaluate the long-term outcome in patients younger than 60 years after total hip arthroplasty using a straight uncemented stem and an uncemented threaded cup. Methods Between 1986 and 1987, 75 hips of 75 patients (mean age, 53.35 ± 6.17 years) were consecutively implanted with an Alloclassic Zweymüller/Alloclassic SL stem and an Alloclassic CSF cup. Forty-four patients had died over the last 30 years. The remaining 31 patients (mean age, 82.9 ± 6.4 years) were reinvited for follow-up examinations. Clinical and radiographic evaluations were carried out. Results At a mean follow-up of 29.5 (28.8–30.2), 4 patients (5.3%) were lost to follow-up. For the endpoint aseptic loosening (defined as the removal of stem or the cup for 2 cases), the overall survival rate is 97.3%. For the endpoint revision for any reason (22 patients), the survival rate is 70.6%. Eleven patients needed an exchange of head and liner, caused by wear. The average time from implantation until change of head and liner was 21.44 years (SD 5.92). Other reasons for revision surgery were septic loosening (3 cases), aseptic loosening of stem and cup (1 case), aseptic loosening of stem (1 case), periprosthetic calcification (2 cases), implant fracture (1 case), periprosthetic fracture (1 case), intraoperative fissure of stem (1 case), and total wear of liner including cup (1 case). Conclusion The combination of a straight stem (Alloclassic) and a screw cup (CSF) shows excellent results in young patients under the age of 60 at ultra-long-term follow-up at 30 years. Revisions due to wear of the polyethylene liner are more likely than in the older patients.

Straight stem and threaded cup in patients under 60 years of age. 28.8-30.2 years of follow-up

Purpose: The aim of this retrospective observational study of one cohort was to evaluate the long-term outcome in patients younger than 60 years after total hip arthroplasty using a straight uncemented stem and an uncemented threaded cup.Methods:Between 1986 and 1987, 75 hips of 75 patients (mean age: 53.35±6.17 years) were consecutively implanted with an Alloclassic Zweymüller/Alloclassic SL stem and an Alloclassic CSF cup. 44 patients had died over the last 30 years. The remaining 31 patients (mean age: 82.9±6.4years) were reinvited for follow-up examinations. Clinical and radiographic evaluations were carried out.Results: At a mean follow-up of 29.5 (28.8-30.2), 4 patients (5.3%) were lost to follow up.For the endpoint aseptic loosening (defined as the removal of stem or the cup for 2 cases), the overall survival rate is 97.3%. For the endpoint revision for any reason (22 patients), the survival rate is 70.6%. Eleven patients needed an exchange of head and liner, caused by wear. The average time from implantation until change of head and liner was 21.44 years (SD 5.92). Other reasons for revison surgery were septic loosening (3 cases), aseptic loosening of stem and cup (1 case), aseptic loosening of stem (1 case), periprosthetic calcification (2 cases), implant fracture (1 case), periprosthetic fracture (1 case), intraoperative fissure of stem (1 case), total wear of liner including cup (1 case).Conclusion: The combination of a straight stem (Alloclassic) and a screw cup (CSF) shows excellent results in young patients under the age of 60 at ultra-longterm follow up at 30 years. Revisions due to wear of the polyethylene liner are more likely than in the older patients.

Straight stem and threaded cup total hip arthroplasty systems in patients under 60 years of age: outdated or still a benchmark? A report on a cohort of 75 patients after 28.8-30.2 years of follow-up

Purpose: The goal of this retrospective observational study of one cohort was to evaluate the long-term outcome in patients younger than 60 years after total hip arthroplasty using a straight uncemented stem and an uncemented threaded cup. Methods: Between 1986 and 1987, 75 hips of 75 patients (mean age: 53.35±6.17 years) were consecutively implanted with an Alloclassic Zweymüller/Alloclassic SL stem and an Alloclassic CSF cup. 44 patients had died over the last 30 years. The remaining 31 patients (mean age: 82.9±6.4years) were reinvited for follow-up examinations. Clinical and radiographic evaluations were carried out. Results: At a mean follow-up of 29.5 (28.8-30.2), 4 patients (5.3%) were lost to follow up. For the endpoint aseptic loosening (defined as the removal of stem or the cup for 2 cases), the overall survival rate is 97.3%. For the endpoint revision for any reason (22 patients), the survival rate is 70.6%. Eleven patients needed an exchange of head and liner due to wear. The mean time from implantation until change of head and liner was 21.44 years (SD 5.92). Other reasons for revisons were septic loosenings (3 cases), aseptic loosening of stem and cup (1 case), aseptic loosening of stem (1 case), periprosthetic calcification (2 cases), implant fracture (1 case), periprosthetic fracture (1 case), intraoperative fissure of stem (1 case), total wear of liner including cup (1 case). Conclusion: The combination of a straight stem (Alloclassic) and a screw cup (CSF) shows excellent results in young patients under the age of 60 at ultra-longterm follow up at 30 years. Revisions due to wear of the polyethylene liner are more likely than in the older patients.