Short stems reproduce femoral offset better than standard stems in total hip arthroplasty: a case-control study

Revision of Failed Short Stems in Total Hip Arthroplasty

Background: The current literature lacks studies which evaluate the failure of short stems in total hip arthroplasty (THA). Therefore, the present clinical investigation reported our experience with the failure of short stems in THA, evaluating the causes of failure, survivorship, and the clinical outcomes of revision arthroplasty. Methods: The present study was performed according to the STROBE guidelines. This study was conducted at the Department of Orthopaedic Surgery of the Humanitas Clinical Institute, Milan, Italy, between 2017 and 2022. All patients who underwent revision surgery of a previously implanted THA using a short stem were prospectively included in the present study. Surgeries were performed with patients in lateral position, using a minimally invasive posterolateral approach. The outcomes of interest were to report information on the type and survivorship of implants used for the revision surgery and evaluate the clinical outcomes and the rate of complications. The following patient-reported outcome measures (PROMs) used for the clinical assessment were the Western Ontario McMaster Osteo-Arthritis Index (WOMAC) and related subscales of pain, stiffness, and function, and the visual analogue scale (VAS). Results: Data from 45 patients were retrieved. Of them, 31% (14 of 45 patients) were women. The mean age was 63.7 ± 13.9 years. The mean length of the implant survivorship was 6.2 ± 5.7 years. In total, 58% (26 of 45 patients) underwent revision of all components, 36% (16 of 45 patients) revised only the stem, and 1% (3 of 45 patients) received a two-stage revision. The mean length of the follow-up was 4.4 ± 1.5 years. The cup was revised in 58% (26 of 45) of patients. At 4.4 ± 1.5 years of follow-up, the WOMAC score was 3.5 ± 1.3 and the VAS was 1.2 ± 1.3. In total, 9% (4 of 45) of patients experienced minor complications. One patient used a walking aid because of reduced function. One patient evidenced muscular hypotrophy. Two patients experienced hip dislocations. All two dislocations were managed conservatively with repositioning in the emergency room under fluoroscopy. No patient needed additional revision surgery or experienced further dislocations. Conclusions: Revision surgery is effective and safe when a short stem THA fails. At approximately four years of follow-up, all patients were highly satisfied with their clinical outcomes. Despite the relatively high number (9%), complications were of a minor entity and were successfully managed conservatively.

Survival and radioclinical evaluation of the Optimys™ short stem at more than 6years' mean follow-up: A retrospective study of 108 cases

INTRODUCTION

The short stems developed in recent years offer an interesting alternative to standard long stems. The Optimys™ short stem has been widely studied, but not according to the National Institute for Health and Care Excellence (NICE) criteria. We therefore conducted a retrospective study of Optimys™ at a minimum 5years' follow-up, to assess: (1) survival on NICE criteria, (2) complications, (3) functional results, and (4) subsidence, restoration of offset and bone remodeling.

HYPOTHESIS

Optimys™ shows survival comparable to that of other non-cemented standard and short stems, with a<0.5% per year revision rate or<2.5% at 5years on NICE criteria.

MATERIAL AND METHODS

A single-center retrospective study included 108 Optimys™ stems at a mean 76.5months' follow-up (range: 60-112months). Clinical [Harris, Oxford-12 and forgotten hip (French version: SHO-12) scores] and radiologic data were collected pre- and postoperatively. Analysis focused on implant survival, complications, functional results and radiological results (restoration of offset, bone remodeling, subsidence and osseointegration) and risk factors for stem migration.

RESULTS

At a mean 76.5months' follow-up (range: 60-112months), Optimys™ survival was 97.7% (95% CI: 0.945-1). Oxford and Harris scores improved significantly: respectively, 16.1 vs. 44.7 [Δ=28.598; 95% CI: 27.410-29.785 (p<0.001)] and 45.3 vs. 95 [Δ=49.662; 95% CI: 47.442-51.882 (p<0.001)]. Mean forgotten hip score (SHO-12) at last follow-up was 82.7±19.6 (range: 35.4-100.0). There was 1 case of aseptic revision at 11months for femoral osseointegration defect. Mean subsidence was 1.64mm (range: 0-20.63mm); no predisposing factors could be identified. Femoral offset increased by a mean 2.41±4.53mm (range: -10.10 to 14.70mm).

CONCLUSION

The present study reports good survival for the Optimys™ stem, which meets NICE criteria. Radiologic and clinical results were encouraging, with a low rate of subsidence, comparable to other series, but with increased femoral offset.

LEVEL OF EVIDENCE

IV; retrospective cohort study.

Femoral antetorsion after calcar-guided short-stem total hip arthroplasty: A cadaver study

Calcar-guided short stems in total hip arthroplasty (THA) permit surgeons to successfully reconstruct postoperative femoroacetabular offset, accurately restore leg length, and adequately re-establish a wide range of caput-collum-diaphyseal angles. However, their effect on femoral antetorsion is less known. Indeed, controlling antetorsion of the femoral stem can be challenging because of the differences in individual femoral geometry and curvature. Therefore, we investigated if calcar-guided short-stem THA alters femoral antetorsion and compared it with conventional-stem THA. Using 12 Thiel-fixed, full-body cadaver specimens from donors without known hip disorders, we compared an uncemented calcar-guided femoral short-stem prosthesis with an uncemented conventional straight-stem prosthesis. In a paired study setup, each specimen received a calcar-guided short stem on one side and a conventional stem on the other. On the acetabular side, all specimens received a press-fit, monobloc acetabular cup. Femoral antetorsion angles were measured using the Waidelich method, and pre- and post-operative angles of both sides were recorded. The mean preoperative femoral antetorsion angles were similar in both groups (24.8°  ± 7.5° vs. 23.8° ± 6.1°, p = 0.313). Mean postoperative femoral antetorsion angles were 23.0° ± 5.5° in short-stem and 13.5° ± 7.1° in conventional-stem hips. Short-stem hips had a small but nonsignificant difference in femoral antetorsion angles pre- and post-operatively (1.8° ± 3.2°, p = 0.109), while the difference for conventional-stem hips was much larger and highly significant (10.3° ± 5.8°, p < 0.001). Calcar-guided short-stem THA effectively restores femoral antetorsion. However, how this affects long-term clinical outcomes and complications warrants further exploration.

A single-surgeon experience in reconstruction of femoro-acetabular offset and implant positioning in direct anterior approach and anterolateral MIS approach with a curved short stem

PURPOSE

Minimally invasive surgery using short stems in total hip arthroplasty gained more popularity. The differences in change of hip offset and implant positioning in minimally invasive approaches are not fully known. Therefore, this study was conducted to evaluate the difference in reconstruction of hip offset and implant positioning in direct anterior approach (DAA) and minimally invasive anterolateral approach (AL MIS).

METHODS

A single surgeon series of 117 hips (117 patients; mean age 65.54 years ± 11.47; index surgery 2014-2018) were included and allocated into two groups: group A (DAA) with 70 hips and Group B (AL MIS) with 47 patients operated. In both groups the same type of cementless curved short hip stem and press fit cup was used.

RESULTS

Both groups showed an equal statistically significant increase of femoral (p < 0.001) and decrease of acetabular offset (p < 0.001). Between both groups no statistically significant difference in offset reconstruction, leg length difference or implant positioning could be found. Leg length increased in both groups significantly and leg length discrepancy showed no difference (group A: - 0.06 mm; group B: 1.11 mm; p < 0.001). A comparable number of cups were positioned outside the target zone regarding cup anteversion.

CONCLUSION

The usage of a curved short stem shows an equal reconstruction of femoro-acetabular offset, leg length and implant positioning in both MIS approaches. The results of this study show comparable results to the existing literature regarding change of offset and restoration of leg length. Malposition of the acetabular component regarding anteversion poses a risk.

Implant positioning in total hip arthroplasty: influence of horizontal and vertical offset on functionality of prosthetic hip joint

PURPOSE

To analyze the effect of implant position measured in terms of offset on patient reported outcomes (PRO) following hip arthroplasty (THA).

METHODS

A total of 243 patients of the total hip replacement who had a one year follow-up were included in the study. Standard both hips radiograph was used to asses post-surgery implant position in terms of horizontal offset and vertical offset, and correlated with functional outcome which was evaluated as change in PRO. i.e., Harris hip score (HHS) post-op. With center of hip rotation as reference, horizontal offset was calculated as sum of distance, of centre, from proximal femoral shaft axis and a vertical line through ipsilateral teardrop, and vertical offset as limb length discrepancy. Post-op patients were classified into three groups depending on the measurement of horizontal offset of the operated hip. The patients having operated hip horizontal offset within 5 mm of the normal hip were grouped as restored offset (RO); those having shorter or higher offset by more than 5 mm compared to normal hip were labeled as decreased (DO) or increased offset (IO) group respectively. The groups were further subdivided into suboptimal and optimal function groups based on HHS, and among these groups, limb length discrepancy was evaluated.

RESULTS

Post follow-up mean HHS (78.23 ± 9.96) improved significantly in all three groups (p < 0.0001). The difference in post-operative HHS among DO, RO, and IO groups was significant, with their averages being 72.5 ± 4.7, 82.1 ± 6.5, and 75.2 ± 4.8 respectively (p = .01). Limb length discrepancy was significantly more common in patients with suboptimal functional scores in all three groups.

CONCLUSION

This study concluded that both horizontal offset and vertical offset should be reconstructed in patients operated with unilateral THR due to hip pathology, since both factor demonstrated a comparable additive effect on clinical outcome.

Reconstruction of the anatomy of the hip in total hip arthroplasty with two different kinds of stems

Background

The reconstruction of the individual anatomy is important in total hip replacement. The aim of the study was to compare two different kinds of stems with respect to the reconstruction of the individual anatomy of the hip.

Methods

We compared the restoration of the anatomical parameters (horizontal and vertical offset, femoral neck-shaft angle (NSA) and leg length) of 100 unilateral CoreHip (CH) implantations with 100 unilateral implantations of a standard anatomical stem (Exception (E)). The CoreHip has three different NSAs and exhibits a constant femoral neck length for the different sizes. The Exception stem has a standard and lateralized version with two different NSAs and, in both versions, the femoral neck length increases proportionately with size. The anatomical parameters of the operated and healthy sides were measured and the differences between the two stems compared.

Results

The horizontal (2.5 ± 2.8 mm (mean ± SD) for CH vs. 5.4 ± 4.1 mm for E, p < 0.001) and vertical offset (4.1 ± 3.5 mm for CH vs. 5.0 ± 3.8 mm, p = 0.024) and femoral neck-shaft-angle (1.7 ± 1.6 degrees for CH vs. 5.6 ± 3.4 degrees for E, p < 0.001) could be reconstructed significantly better with the CoreHip system. There was a tendency for the leg length (4.0 ± 3.9 mm for CH vs. 4.5 ± 3.8 mm; p = 0.11) to be better restored with the CoreHip.

Conclusion

The reconstruction of the individual anatomy of the hip with an endoprosthesis could be realized significantly better with the stem that was designed with three different femoral neck-shaft angles and a constant femoral neck length over different sizes.

Femoroacetabular offset restoration in total hip arthroplasty; Digital templating a short stem vs a conventional stem

BACKGROUND

Failure in restoring individual anatomy could be a reason for persistent functional limitations post total hip arthroplasty. Femoroacetabular offset (FAO) plays an important role in anatomic restoration, as loss of offset ≥ 5 mm is associated with altered gait and decreased functional outcome. Preoperative assessment by use of digital templating has shown to be a reliable method for sizing the components in total hip arthroplasty, and can show if anatomic restoration is achieved. In recent years, short stems are growing in popularity as it could allow better restoration due to more variety in placement.

AIM

To assess whether restoration of the FAO differs between a short or a conventional stem by use of digital templating. Additionally, association of the preoperative offset and caput-colllum-diaphyseal angle (CCD-angle) within restoration of both stems was investigated, and the reliability of measurements was assessed.

METHODS

A total of 100 standardized hip radiographs were used for digital templating. Restoration of FAO was classified into “restored” or “not restored”, when a < 5 mm or ≥ 5 mm difference from baseline value presented, respectively. Differences between the two stems concerning proportions of correct restoration of the FAO were analyzed by use of McNemar tests. To assess association between CCD-angle and preoperative FAO with absolute FAO restoration, multi-level analysis was performed by use of a linear mixed model to account for paired measurements. Through determination of the optimal point under the curve in operating curve-analysis, bootstrapping of thousand sets was performed to determine the optimal cutoff point of the preoperative FAO for restoration within the limits of 5 mm. Three observers participated for inter-observer reliability, with two observers measuring the radiographs twice for intra-observer reliability.

RESULTS

The mean preoperative FAO was 79.7 mm (range 62.5-113 mm), with a mean CCD-angle of 128.6° (range 114.5°-145°). The conventional stem could only restore the FAO in 72 of the cases, whereas the short stem restored the FAO in all cases. CCD-angle was not a predictor, but the preoperative FAO was. A cut-off point of 81.25 mm (95% confidence interval of 80.75-84.75 mm) in preoperative FAO was found where the conventional stem was unable to restore the FAO. Reliability of measurements was excellent, with an intra-observer reliability of 0.99 and inter-observer reliability in baseline measurements higher than 0.9 between the three observers.

CONCLUSION

In preoperative planning of FAO restoration in total hip arthroplasty, digital templating shows that short stems with a curve following the medial calcar are potentially better at restoring the FAO compared to conventional stems if the preoperative offset is ≥ 80.0 mm.

Hip implants can restore anatomical and medialized rotation centres in most cases : a 3D templating study comparing four implantation strategies

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.

The impact of reducing the femoral stem length in total hip arthroplasty during gait

AIM

The length of the femoral stem in total hip arthroplasty (THA) is a practical consideration to prevent gait impairment. The aim of this study was to determine if reducing the femoral stem length in THA would lead to impaired gait biomechanics.

METHODS

Patients uniformly with the same brand implant of differing lengths (100 mm vs 140-166 mm) were taken retrospectively from a prospective trial introducing a new short stem. Twelve patients without any other disorder to alter gait besides contralateral differing length stem THA were tested at differing gradients and speed on a validated instrumented treadmill measuring ground reaction forces. An anthropometrically similar group of healthy controls were analysed to compare.

RESULTS

With the same posterior surgical approach, the offset and length of both hips were reconstructed within 5 mm of each other with an identical mean head size of 36 mm. The short stem was the last procedure for all the hips with gait analysis occurring at a mean of 31 and 79 months postoperatively for the short and long stem THA, respectively. Gait analysis between limbs of both stem lengths demonstrated no statistical difference during any walking condition. In the 90 gait assessments with three loading variables, the short stem was the favoured side 51% of the time compared 49% for the long stem.

CONCLUSION

By testing a range of practical walking activities, no lower limb loading differences can be observed by reducing the femoral stem length. A shorter stem demonstrates equivalence in preference during gait when compared to a reputable conventional stem in total hip arthroplasty.

Bone remodelling and integration of two different types of short stem: a dual-energy X-ray - absorptiometry study

PURPOSE

Different kinds of bone preserving hip stems have been created to assure a more physiological distribution of the strengths on the femur. The aim of this research is to evaluate the density reaction of the periprosthetic bone while changing the conformation of the prosthetic implant on dual-energy X-ray - absorptiometry (DXA).

METHODS

This is a prospective, single-centre study assessing bone remodelling changes after implantation of two short hip stems, dividing the patients in two groups according to the implant used: 20 in group A, Metha (B-Braun), and 16 in group B, SMF (Smith and Nephew). All participants had a pre-operative and a post-operative (24 months) DXA evaluating the changes in bone mass density (BMD) occurred in the five Gruen's zones.

RESULTS

Compared to the pre-operative value, differences in BMD percentage were statistically significant only in ROI 4 (p < 0.05), with an increase in both groups (9 and 18%, respectively). The average increase in BMD was of 7.3% and 7.2% in the 2 groups.

CONCLUSION

According to our study, both stems have proved able to provide good load distribution across the metaphyseal region favouring proper system integration. Nonetheless, is certainly needed to perform other studies with longer follow-up and bigger populations to give strength to these conclusions.

Optimizing leg length correction in total hip arthroplasty

PURPOSE

Residual feeling of leg length discrepancy (LLD) is a common cause of patient dissatisfaction following total hip arthroplasty (THA). The purpose of this study is to propose a method for determining an optimal leg length correction goal in THA.

METHODS

We conducted a retrospective study of 132 patients to examine the radiographic LLD (R-LLD), perceived LLD (P-LLD), and whether or not the patient has an uncomfortable feeling about the leg length after THA.

RESULTS

The residual discomfort rate in all patients was 9.1% (12/132 patients), and ten of these 12 patients felt uncomfortable due to a longer leg length. When R-LLD was within 7 mm, the rate was 6.8% (8/118 patients), which is nearly equal to the rate of 7.8% (5/64 patients) in cases in which R-LLD was within 2 mm. On the other hand, when R-LLD was 8 mm or more, the rate was 57.1% (4/7 patients).

CONCLUSIONS

The results of our study show that 7 mm may be a reasonable threshold for reducing the residual discomfort. However, even with little or no R-LLD, some patients will continue to experience discomfort. We think that this is because of pre-operative differences between R-LLD and P-LLD in such cases. If the patient has a pelvic declination on the affected hip side and a lumbar scoliosis angle that is convex toward the affected hip side before surgery, the ideal length may be a little shorter than the radiographic isometry, since such patients are likely to feel a longer leg length than that shown radiographically.