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.

5-Year Clinical and Radiographic Results of the Direct Anterior Approach for Total Hip Arthroplasty Using a Collared Cementless Femoral Short-Stem Prosthesis

The aim of this study was to investigate the radiological and clinical outcome of the direct anterior approach (DAA) in total hip arthroplasty (THA) using a collared cementless femoral short-stem. This retrospective study included 124 patients with 135 THAs operated from 2014 to 2016 using a collared cementless triple tapered hydroxyapatite-coated femoral short-stem (AMIStem H Collared®, Medacta International, Castel San Pietro, Switzerland) implanted with a DAA. Follow-up was performed at three months, 12 months, and five years. Clinical outcome was assessed using the hip osteoarthritis outcome score (HOOS) and radiological analysis was done using conventional radiographs, which included evaluation of the femur morphology based on Dorr classification, of radiolucencies based on the Gruen zone classification and of stem subsidence. The mean age was 67.7 ± 11.3 years and the mean body mass index (BMI) was 27.4 ± 4.4 kg/m2. The stem survival rate at five years was 99.1% with one revision due to recurrent dislocations. Mean HOOS score improved from 40.9 ± 18.3 preoperatively to 81.5 ± 19.7 at three months, 89.3 ± 10.9 at 12 months, and 89.0 ± 14.0 at five years (all with p < 0.001). No significant correlations were found between age, femoral bone morphology, BMI and HOOS, and the appearance of relevant radiolucencies.

More than a feeling?—Overruling the preoperatively templated offset option leads to a minor offset increase in short stem total hip arthroplasty

Purpose Short stems are increasingly used in total hip arthroplasty (THA) because of advantages in bone and soft tissue preservation and reconstruction of hip geometry. Digital templating is essential in determining the correct offset option and stem size in THA. However, the preoperative template sizes might be intraoperatively overruled. Patients and methods We evaluated the effect of intraoperative overruling of the preoperatively templated offset option of a short curved stem on hip offset, leg length, implant positioning, and femoral canal fill index. The overruling was performed in case of intraoperative instability, telescoping, or both. A series of 1052 consecutive THAs with a cementless short curved stem and press-fit cup was retrospectively screened. One hundred patients with unilateral THA and a contralateral native and morphologically healthy hip as a reference met the inclusion criteria. Measurements were carried out on preoperative and 3 months anterior–posterior postoperative radiographs. Patients were divided according to the overruling by offset option or stem size. Results Hip offset was increased in all groups, but only with significant increase if an offset option + 1 was used intraoperatively (p = 0.025). LLD was restored without significance in all groups (p = 0.323; p = 0.157). Conclusion Intraoperative overruling of the preoperative digital template in cementless short stem total hip arthroplasty results in an increase of hip offset compared to a contralateral healthy hip. However, the increase is marginal and clearly under 5 mm compared to the contralateral healthy hip.

The morphology of the proximal femur in cementless short-stem total hip arthroplasty: No negative effect on offset reconstruction, leg length difference and implant positioning

Background Correct reconstruction of hip offset (HO) and leg length are important for clinical–functional outcome and patient satisfaction in total hip arthroplasty (THA). The morphology of the proximal femur can pose a risk for increased leg length difference (LLD) in cementless straight-stem THA. We therefore wanted to evaluate, if this is also applicable in THA with a cementless meta-diaphyseal short stem. Methods In a retrospective study, 106 patients (index surgery 2014–2019) with unilateral THA and a morphologically healthy hip as a reference (Kellgren–Lawrence ≤ 1) were included. The same cementless short stem with meta-diaphyseal fixation and cementless press-fit cup was implanted. The proximal femur was rated by Dorr’s classification, and subgroups were formed afterward. Measurements were carried out on preoperative and 3 months postoperative anterior–posterior radiographs of the pelvis. Kruskal–Wallis test, Fisher’s exact test and binary logistic regression were performed to evaluate the influence of the anatomical shape on postoperative leg length difference and offset reconstruction. Results The Dorr type did not show any significance influence on LLD (p = 0.532), or postoperative difference in femoral offset (p = 0.243), acetabular offset (p = 0.106) and hip offset (p = 0.698). Stem alignment (p = 0.705) and canal fill indices (CFI I: p = 0.321; CFI II: p = 0.411; CFI III: p = 0.478) were also without significant differences. Logistic regression did not show any significant increased risk for a LLD ≥ 5 mm or ≥ 10 mm as well as HO ≥ 5 mm or ≥ 10 mm. Conclusion Reconstruction of hip offset and postoperative leg length difference is not negatively influenced by Dorr type, canal flare index, cortical index and canal-to-calcar ratio in cementless short-stem THA. Implant positioning and canal fill are also not negatively affected by the anatomical shape of the proximal femur. Level of evidence: Level IV.

Peri-prosthetic Bone Remodeling of Hydroxyapatite-coated Compaction Short Stem was Not Affected by Stem Alignment

Background: We aimed to investigate the relationship between stem insertion alignment and postoperative bone mineral density (BMD) changes in patients with full hydroxyapatite-coated (HA) compaction short stem and short tapered-wedge stem. Methods: This retrospective cohort study enrolled 115 consecutive patients (115 joints) undergoing total hip arthroplasty (THA) using the full HA compaction short (n=59) and short tapered-wedge (n=56) stems. Stem alignment including anteversion, valgus, and anterior tilt were measured by 3D-template using computed tomography (CT) data. Post-operative peri-prosthetic BMD was measured by dual-energy X-ray absorptiometry (DEXA). The relationship between stem alignment and BMD changes in the stems were analyzed.Results: Both groups showed similar patterns of peri-prosthetic BMD changes. Stem insertion alignments of anteversion, valgus, and anterior tilt were different between the two types of stems. Stem alignment of valgus and anterior tilt did not affect peri-prosthetic BMD in either type of stem. An absolute anteversion difference between stem anteversion and original canal anteversion caused significant peri-prosthetic BMD loss in Gruen zones 1 and 7 in the tapered-wedge stem. However, stem alignment of absolute anteversion difference did not affect BMD changes in the HA compaction stem.Conclusion: Peri-prosthetic bone remodeling remained unaffected by stem alignment after THA with the new short full HA compaction stem.

Clinical and radiographic outcomes after total hip arthroplasty with the NANOS neck preserving hip stem: a 10 to 16-year follow-up study

Background Short-stem Hip Arthroplasty (SHA) are increasingly implanted in recent years thanks to their potential advantage in preserving metaphyseal bone-stock. Among them, the NANOS® short-stem implant demonstrated satisfactory results to short and mid-term. The purpose of this retrospective study was to evaluate the clinical and radiographic outcome of the Nanos® short stem at a minimum follow-up of 10 years. Methods Sixty-seven patients aged 53 ± 20 years were enlisted in the study, for a total of 72 hips. Primary outcomes were survivorship of the implant and clinical outcome measured using the Hip disability and Osteoarthritis Outcome scores (HOOS) and the Short Form Survey (SF12) questionnaire. The secondary outcome was a radiological evaluation calculating the inclination and the anteversion angle of the acetabular cup for each implant and investigating osteolysis, heterotopic ossifications and stem position. Results We observed a 95.5% stem survivorship. The complication rate was 7.6% and three implants underwent revision because of an aseptic loosening, an infection and a periprosthetic fracture due to trauma. Among 58 patients (63 hips) evaluated in an outpatient visit 10–16 years after surgery, improvement in clinically relevant scores comparing with baseline was observed: HOOS score increased after surgery in all its subcategories (from 32.25 ± 14.07% up to 91.91 ± 9.13%) as well as SF12 which increased by more than 18 percentage points. On clinical assessment, the range of motion (ROM) was restored at follow-up, 1 patient (1.7%) showed a squeaking hip and 2 (3.4%) reported leg-length discrepancy. Neutral stem positioning was achieved in 58 hips and heterotopic ossifications occurred in 10 hips (16%). Conclusions The current study reports good clinical and radiological outcomes following NANOS® short-stem hip implant at minimum 10 years-follow-up. Since the high rate of stem survivorship, the low complication rate demonstrated and the overall patient satisfaction, our results suggest NANOS® neck-preserving prostheses should be considered as a valid alternative to standard implants.