Combined anteversion technique for total hip arthroplasty

Intraoperative estimation of natural femoral anteversion from proximal femoral osseous orientation during total hip arthroplasty

BACKGROUND

The purpose of this study was to elucidate the relationship between the orientation of the osseous structure of the proximal femur encountered during total hip arthroplasty (THA) and preoperative femoral anteversion (FA).

METHODS

Three-dimensional models were constructed using full-length lower extremity computed tomography images from a total of 80 participants. Femoral neck cutting was performed at heights of 5, 10, and 15 mm relative to the lesser trochanter. Following neck cutting, the angles formed by the anterior outer cortex and posterior outer cortex with the posterior condylar line (PCL) were defined as the anterior cortical angle (ACA) and posterior cortical angle (PCA), respectively. Univariate linear regression analysis was conducted using the remaining measurements with FA as the dependent variable.

RESULTS

The mean age of the participants was 60.98 ± 10.82 years (males, 60.50 ± 11.36 years; females, 61.45 ± 10.37 years) (p = 0.697). All cortical angles and FA were larger in women compared to those in men. When comparing measurements by age groups, no statistically significant differences were observed. Univariate linear regression analysis with FA as the dependent variable showed statistical significance for all cortical angles. The adjusted R2 values were 0.711 (ACA5), 0.677 (ACA10), 0.572 (ACA15), 0.493 (PCA5), 0.574 (PCA10), and 0.446 (PCA15).

CONCLUSION

Natural FA can be inferred from the anterior cortical angle (ACA) from femoral neck cutting plane observed during the THA procedure without preoperative images.

TRIAL REGISTRATION

Retrospectively registered.

Evaluation of Two Clinical Stem Fit Philosophies within the Femoral Canal Using a Preoperative Planning Tool: Could a Hybrid Approach Be Best?

BACKGROUND

Total hip arthroplasty (THA) has transformed patient lives, yet evolving expectations and the number of postoperative foot angle changes have underscored the need for precise component positioning. The objective of this study was to use three-dimensional (3D) preoperative planning to evaluate stem alignment and orientation for three THA systems using two different stem fit algorithms. It was hypothesized that the different stem alignments would yield similar changes in stem orientation and placement within the canal for all three systems.

METHOD

This study introduced a novel 3D preoperative planning tool, comparing two different surgical stem fit philosophies within the canal: "canal fit" (CF) and "anatomical fit" (AF). We virtually implanted ten subjects with three different THA implant systems using both philosophies, evaluating 60 total fits within the canals. The "canal fit" philosophy aimed to minimize cortical bone removal. In contrast, the "anatomical fit" philosophy prioritized aligning the implanted head with the anatomical head center.

RESULTS

Detailed analyses revealed that AF led to fixation occurring mainly on the medial aspect of the stem, while CF exhibited a more even distribution between medial and lateral sides. The AF philosophy achieved significantly closer placement of the implanted head to the anatomical center (2.0 to 2.1 mm) compared to the CF philosophy (3.0 to 6.0 mm) (P < 0.01). The AF resulted in neutral stem orientation (0°) across all stems, whereas the CF exhibited greater malrotation (2.0 to 7.0°) (P < 0.02). The AF required more bone removal (0.13 to 0.46 cm³) than the CF (0.02 to 0.06 cm³) (P < 0.01).

CONCLUSION

The findings underscore the importance of 3D planning, emphasizing its potential to improve stem version alignment in THA. The results from this study may advocate 3D preoperative planning with robotic surgery to plan stem placement within the canal while maintaining anatomical femoral head restoration.

Error of intraoperative measurement of stem anteversion is decreased by measuring in neutral hip position during total hip arthroplasty

BACKGROUND

Intraoperative stem anteversion, which is the angle between the lower leg axis and the trial-stem axis with hip flexion and adduction, is generally evaluated by the surgeon's visual estimation during total hip arthroplasty (THA). However, the conventional approach can be influenced by knee osteoarthritis or uncertain surgeon's observation point. Therefore, we developed a new method for measuring the stem anteversion angle in the neutral hip position using an original rod attached to the trial-stem perpendicular to the long axis and parallel to the stem neck. This study aimed to assess the accuracy of our method in comparison with the conventional method of measuring intraoperative stem anteversion angle.

METHODS

We measured the intraoperative stem anteversion angle in consecutive 106 hips of 106 patients who underwent cementless primary THA with a tapered wedge stem. Absolute error in the stem anteversion angle was expressed as the difference between intraoperative (common vs. neutral hip positions) and postoperative computed tomography measurements, i.e., true stem anteversion. Additionally, we investigated the factors affecting these errors.

RESULTS

The absolute error of measurement was significantly smaller in the neutral hip position than in the common position (3.0° ± 2.5° vs. 8.0° ± 3.9°; p < 0.0001). The factor associated with the error was advanced knee osteoarthritis in the common position, whereas it was not statistically significant in the neutral hip position.

CONCLUSIONS

This study suggests that the error in the intraoperative measurement of stem anteversion is decreased by measuring in the neutral hip position during THA.

Two-Dimensional Versus Three-Dimensional Preoperative Planning in Total Hip Arthroplasty

BACKGROUND

Preoperative planning in total hip arthroplasty (THA) involves utilizing radiographs or advanced imaging modalities, including computerized tomography scans, for precise prediction of implant sizing and positioning. This study aimed to compare 3-dimensional (3D) versus 2-dimensional (2D) preoperative planning in primary THA with respect to key surgical metrics, including restoration of the horizontal and vertical center of rotation (COR), combined offset, and leg length.

METHODS

This study included 60 patients undergoing primary THA for symptomatic hip osteoarthritis (OA), randomly allocated to either robotic arm-assisted or conventional THA. Digital 2D templating and 3D planning using the robotic software were performed for all patients. All measurements to evaluate the accuracy of templating methods were conducted on the preoperative computerized tomography scanogram, using the contralateral hip as a reference. Sensitivity analyses explored differences between 2D and 3D planning in patients who had superolateral or medial OA patterns.

RESULTS

Compared to 2D templating, 3D templating was associated with less medialization of the horizontal COR (-1.2 versus -0.2 mm, P = .002) and more accurate restoration of the vertical COR (1.63 versus 0.3 mm, P < .001) with respect to the contralateral side. Furthermore, 3D templating was superior for planned restoration of leg length (+0.23 versus -0.74 mm, P = .019). Sensitivity analyses demonstrated that in patients who had medial OA, 3D planning resulted in less medialization of horizontal COR and less offset reduction. Conversely, in patients who had superolateral OA, there was less lateralization of horizontal COR and less offset increase using 3D planning. Additionally, 3D planning showed superior reproducibility for stem, acetabular cup sizes, and neck angle, while 2D planning often led to smaller stem and cup sizes.

CONCLUSIONS

Our findings indicated higher accuracy in the planned restoration of native joint mechanics using 3D planning. Additionally, this study highlights distinct variances between the 2 planning methods across different OA pattern subtypes, offering valuable insights for clinicians employing 2D planning.

A Novel Device for Intraoperative Measurement of Stem Anteversion Angle in Total Hip Arthroplasty

Background

Stem anteversion plays a crucial role in mitigating postoperative complications in total hip arthroplasty (THA). The application of the combined-anteversion theory in THA necessitates the intraoperative measurement of the stem anteversion angle (SAA). However, estimating SAA intraoperatively poses challenges for surgeons lacking a computer-assisted navigation system. In this study, we assessed the precision of intraoperative SAA measurements using a recently developed device, comparing them with 3-dimensional measurements obtained from postoperative computed tomography.

Methods

We examined 127 hips in 127 patients who underwent unilateral THA at our institution. Employing our newly constructed device, attachable to rasping broach handles, we measured the SAA intraoperatively. This process involved incorporating the correction angle derived from the preoperative epicondylar view. We then compared the postoperative SAA with the intraoperative measurements, both with and without the correction angle, to ascertain the device's utility.

Results

The device yielded an intraoperative SAA measurement of 17.93 ± 7.53°. In contrast, the true SAA measured on postoperative computed tomography was 26.40 ± 9.73°. The discrepancy between intraoperative and true SAA was 8.94 ± 5.44° (without the correction angle) and 4.93 ± 3.85° (with the correction angle). Accuracy within a discrepancy of <5° was achieved in 77 cases (60.6%), and <10° was achieved in 113 cases (89.0%). The accuracy remained consistent regardless of the stem-placement angle (varus/valgus, or flexion/extension) or the presence of ipsilateral knee osteoarthritis.

Conclusions

The SAA-measuring device, attachable to various rasping handles, proves useful for straightforward, cost-effective, and noninvasive intraoperative SAA measurement during THA.

Do all short stem types restore biomechanical parameters of the hip? Comparison according to femoral neck osteotomy levels

PURPOSE

There is no consensus on ideal short femoral stem design. A classification system proposed by Feyen and Shimmin divides short stems in two types according to femoral neck osteotomy levels: subcapital (IIIA) and standard (IIIB). The study aims to determine which design type is more successful in restoring native biomechanical parameters and whether stem type has an impact on clinical results.

METHODS

In this retrospective comparative study, patients that have undergone short stem hip arthroplasty were evaluated according to stem types: type IIIA (n = 52, 66.7%) (Mathys Optimys) and IIIB (n = 26, 33.3%) (Implantcast Aida and Smith & Nephew SMF). Pelvis X-rays were assessed in terms of femoral neck length, horizontal and vertical hip centres of rotation, horizontal and vertical femoral offsets, abductor lever arm lengths, leg lengths, and stem-shaft angles. Improvement in Harris hip scores, differences between post-operative and pre-operative measurements, and stem-shaft angles were evaluated and compared between two groups.

RESULTS

Mean femoral neck resection (8.27 ± 6.68 mm in IIIA and 15 ± 6.33 mm in IIIB) was significantly different between both groups (p < 0.001). Harris hip scores were increased at post-operative six months in both groups with no difference (84.4 ± 6.4 and 84.6 ± 5.5, p = 0.4). The absolute values of differences between pre-operative and post-operative horizontal centres of rotation (p = 0.63), vertical centers of rotation (p = 0.75), horizontal femoral offsets (p = 0.78), vertical femoral offsets (p = 0.83), abductor lever arm distances (p = 0.63), and leg length (p = 0.21) measurements were not different between both groups. Stem positions were both varus with no statistically significant difference between groups (p = 0.14).

CONCLUSION

We found no difference regarding restoration of biomechanical parameters between short stem designs with different levels of neck osteotomy. Additionally, short stem can mostly result in varus component positioning regardless of the level of neck osteotomy.

Dislocation of primary total hip arthroplasty: Analysis of risk factors and preventive options

Total hip arthroplasty (THA) is one of the most successful elective operations in orthopedic surgery for improving pain and functional disability in patients with end-stage joint disease. However, dislocation continues to be a troublesome complication after THA, as it is a leading cause of revision and is associated with substantial social, health, and economic costs. It is a relatively rare, usually early occurrence that depends on both the patients' characteristics and the surgical aspects. The most recent and important finding is the special attention to be given preoperatively to spinopelvic mobility, which is closely related to the incidence of dislocation. Consequently, clinical and radiographic assessment of the lumbar spine is mandatory to identify an altered pelvic tilt that could suggest a different positioning of the cup. Lumbar spinal fusion is currently considered a risk factor for dislocation and revision regardless of whether it is performed prior to or after THA. Surgical options for its treatment and prevention include the use of prostheses with large diameter of femoral head size, dual mobility constructs, constrained liners, and modular neck stems.

Stem anteversion is not affected by proximal femur geometry in robotic-assisted total hip arthroplasty

BACKGROUND

In the present study, the surgeon aimed to align the stem at 5° to 25° in anteversion. The robotic technology was used to measure stem anteversion with respect to proximal femur anteversion at different levels down the femur.

METHODS

A total of 102 consecutive patients underwent robotic-arm-assisted total hip arthroplasty (RTHA). 3D CT-based preoperative planning was performed to determine femoral neck version (FNV), posterior cortex anteversion (PCA), anterior cortex anteversion (ACA), and femoral metaphyseal axis anteversion (MAA) at 3 different levels: D (10 mm above lesser trochanter), E (the midpoint of the planned neck resection line) and F (head-neck junction). The robotic system was used to define and measure stem anteversion during surgery.

RESULTS

Mean FNV was 6.6° (SD: 8.8°) and the mean MAA was consistently significantly higher than FNV, growing progressively from proximal to distal. Mean SV was 16.4° (SD: 4.7°). There was no statistically significant difference (P = 0.16) between SV and MAA at the most distal measured level. In 96.1% cases, the stem was positioned inside the 5°-25° anteversion range.

CONCLUSIONS

Femoral anteversion progressively increased from neck to proximal metaphysis. Aligning the stem close to femoral anteversion 10 mm above the lesser trochanter often led to the desired component anteversion.

Roles of combined femoral and acetabular anteversion in pathological changes of hip dysplasia and hip reconstructive surgery

Combined femoral and acetabular anteversion is the sum of femoral and acetabular anteversion, representing their morphological relationship in the axial plane. Along with the increasing understanding of hip dysplasia in recent years, numerous scholars have confirmed the role of combined femoral and acetabular anteversion in the pathological changes of hip dysplasia. At present, the reconstructive surgery for hip dysplasia includes total hip replacement and redirectional hip preservation surgery. As an important surgery index, combined femoral and acetabular anteversion have a crucial role in these surgeries. Herein, we discuss the role of combined femoral and acetabular anteversion in pathological changes of hip dysplasia, total hip replacement, and redirectional hip preservation surgery.

Combining inertial navigation with transacetabular ligament in total hip arthroplasty via direct anterior approach results in excellent accuracy compared to standard manual technique - A retrospective cohort study

BACKGROUND

Correct acetabular component placement plays a critical role in reducing early revisions after dislocations in total hip arthroplasty (THA). Although the transverse acetabular ligament (TAL) guides anteversion, inclination can only be accurately guided by navigation. In order to overcome the initial disadvantages with navigation, an imageless, easy-to-use inertial navigation system has been recently introduced. This study aims to analyze the accuracy of inclination with this navigation system compared to the standard manual technique.

METHODS

Two cohorts, manual technique (MT) and navigation (NAV) cohorts, consisted of 83 and 95 patients, respectively, after exclusion criteria were applied. Inclination target was 38° and anteversion was guided by TAL. Demographic data were collected, and anteroposterior (AP) pelvic and cross-table lateral radiographs were obtained 6 weeks post-operatively. Inclination and anteversion were determined on the AP pelvic and cross-table lateral radiograph, respectively.

RESULTS

A mean inclination of 41.8° (±6.8°) and 38.9° (±4.4°) was found in the MT and NAV cohorts, respectively. There was no statistical difference in gender, age, and BMI. If the inclination was set within 10° of the target (i.e., 38°), 88% of the MT cohort and 97% of the NAV cohort were within the target zone. Accuracy decreased to 53% and 83%, respectively, if the target zone range was narrowed down to ± 5°.

CONCLUSION

Combining inertial imageless navigation for inclination and TAL as a landmark for anteversion is significantly more accurate compared to the manual technique, without having the limitations and disadvantages of current standard navigational techniques.

Clinical effects of combined anteversion and offset on postoperative dislocation in total hip arthroplasty

BACKGROUND

Implant impingement and soft tissue tension are factors involved in dislocation after total hip arthroplasty (THA). Combined anteversion (CA) has been used as an indicator for implant placement. However, optimal implant placement remains a challenge. Moreover, the effect of changes in offset on dislocation is still unclear. In this study, we aimed to clarify the effects of postoperative CA and pre- and postoperative changes in offset on dislocation.

METHODS

Included were patients who underwent primary cementless THA between 2013 and 2020. The mean values of CA and offset in the dislocation and non-dislocation groups were compared. The CA values within ± 10% of the recommended values were defined as good CA, and those outside the range were rated as poor CA. The dislocation rates were compared between the good and poor CA groups and between the groups with and without increased offset.

RESULTS

A total of 283 hips were included. The mean values of CA in the dislocation and non-dislocation groups were significantly different (P < 0.05). The dislocation rate was significantly lower in the good CA group (P < 0.05). The dislocation rates in the groups with and without increased total offset were 0.5% and 4.3%, respectively (P = 0.004). There were no dislocations in patients with good CA and increased offset.

CONCLUSIONS

The dislocation rate was significantly lower when implants were placed within ± 10% of the recommended CA value. Our results suggest that dislocation can be avoided by placing the implant in the good CA range and considering the increase in total offset on the operative side.

A New Method to Predict Postoperative Stem Anteversion in Total Hip Arthroplasty for Developmental Dysplasia of the Hip

BACKGROUND

Preoperative evaluation of femoral anteversion to predict postoperative stem anteversion aids the selection of an appropriate prosthesis and optimizes the combined anteversion in total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH). The conventional prediction methods are based on the femoral anteversion measurement at the location of the femoral head and/or neck. However, varied differences between femoral anteversion and postoperative stem anteversion were demonstrated. This study investigated the predictive role of a new method based on the principle of sagittal three-point fixation.

METHODS

From January 2017 to December 2018, a total of 133 DDH hips that underwent THA were retrospectively analyzed. There were 76 Crowe type I, 27 type II, and 30 type III hips. The single-wedge stem was used in 49 hips, and the double-wedge stem was used in 84 hips. Preoperative native femoral anteversion at the femoral head-neck junction, anterior cortex anteversion at 2 levels of the lesser trochanter, posterior cortex anteversion at 5 levels of the femoral neck, and postoperative stem anteversion were measured using two-dimensional computed tomography. Predictive anteversion by the new method was calculated as the average anteversion formed by the anterior cortex at the lesser trochanter and the posterior cortex at the femoral neck.

RESULTS

For hips with different neck heights, different Crowe types, different stem types, or different femoral anteversions, native femoral anteversion showed widely varied differences and correlations with stem anteversion, with differences ranging from -1.27 ± 8.33° to -13.67 ± 9.47° and correlations ranging from 0.122 (p = 0.705, no correlation) to 0.813. Predictive anteversion formed by the anterior cortex at the lesser trochanter proximal base and posterior cortex 10 mm above the lesser trochanter proximal base showed no significant difference with stem anteversion, with less varied differences (0.92 ± 7.52°) and good to excellent correlations (r = 0.826).

CONCLUSION

Adopting our new method, predictive anteversion, measured as the average anteversion of the anterior cortex at the lesser trochanter proximal base and posterior cortex 10 mm above the lesser trochanter proximal base, predicted postoperative stem anteversion more reliably than native femoral anteversion.

A new designed full process coverage robot-assisted total hip arthroplasty: a multicentre randomized clinical trial

OBJECTIVE

To compare the effect of a new complete robot-assisted total hip arthroplasty (RA-THA) with that of the manual total hip arthroplasty (MTHA) and to verify the accuracy and safety of the former.

METHODS

Overall, 148 patients were enroled from 3 March 2021 to 28 December 2021 in this study and classified into RA-THA ( n =74 patients) and MTHA ( n =74 patients) groups. The sex, age, operative side, BMI, diagnosis, other basic information, operative time, acetabular prosthesis anteversion and inclination, femoral prosthesis anteversion and angulation, femoral prosthesis filling rate, leg length discrepancy (LLD), Harris hip score, and visual analogue scale (VAS) score of the two groups were compared.

RESULTS

No significant differences were observed in the two groups regarding sex, age, operative side, BMI, diagnosis, Harris hip score, VAS score, acetabular inclination, acetabular prosthesis anteversion, femoral prosthesis anteversion, combined anteversion, and femoral prosthesis filling rate ( P >0.05). The operative time was significantly longer in the RA-THA group than in the MTHA group (106.71±25.22 min vs. 79.42±16.16 min; t=7.30, P <0.05). The femoral angulation (1.78°±0.64°) and LLD (2.87±1.55 mm) in the RA-THA group were significantly lesser than those in the MTHA group (2.22°±1.11° and 5.81±6.27 mm, respectively; t=-2.95 and t=-3.88, P <0.05).

CONCLUSION

The complete RA-THA has some advantages over the traditional procedure in restoring the lower limb length and controlling the femoral prosthesis angulation. Thus, this study verifies the accuracy and safety of the robot-assisted system.

A prospective randomized controlled trial comparing CT-based planning with conventional total hip arthroplasty versus robotic arm-assisted total hip arthroplasty

Aims

Achieving accurate implant positioning and restoring native hip biomechanics are key surgeon-controlled technical objectives in total hip arthroplasty (THA). The primary objective of this study was to compare the reproducibility of the planned preoperative centre of hip rotation (COR) in patients undergoing robotic arm-assisted THA versus conventional THA.

Methods

This prospective randomized controlled trial (RCT) included 60 patients with symptomatic hip osteoarthritis undergoing conventional THA (CO THA) versus robotic arm-assisted THA (RO THA). Patients in both arms underwent pre- and postoperative CT scans, and a patient-specific plan was created using the robotic software. The COR, combined offset, acetabular orientation, and leg length discrepancy were measured on the pre- and postoperative CT scanogram at six weeks following surgery.

Results

There were no significant differences for any of the baseline characteristics including spinopelvic mobility. The absolute error for achieving the planned horizontal COR was median 1.4 mm (interquartile range (IQR) 0.87 to 3.42) in RO THA versus 4.3 mm (IQR 3 to 6.8; p < 0.001); vertical COR mean 0.91 mm (SD 0.73) in RO THA versus 2.3 mm (SD 1.3; p < 0.001); and combined offset median 2 mm (IQR 0.97 to 5.45) in RO THA versus 3.9 mm (IQR 2 to 7.9; p = 0.019). Improved accuracy was observed with RO THA in achieving the desired acetabular component positioning (root mean square error for anteversion and inclination was 2.6 and 1.3 vs 8.9 and 5.3, repectively) and leg length (mean 0.6 mm vs 1.4 mm; p < 0.001). Patient-reported outcome measures were comparable between the two groups at baseline and one year. Participants in the RO THA group needed fewer physiotherapy sessions postoperatively (median six (IQR 4.5 to 8) vs eight (IQR 6 to 11; p = 0.005).

Conclusion

This RCT suggested that robotic-arm assistance in THA was associated with improved accuracy in restoring the native COR, better preservation of the combined offset, leg length correction, and superior accuracy in achieving the desired acetabular component positioning. Further evaluation through long-term and registry data is necessary to assess whether these findings translate into improved implant survival and functional outcomes.

Femoral Neck Anteversion: Which Distal Femur Landmark Matters?

Background

Femoral neck anteversion has traditionally been measured by the angle between the distal femur posterior condylar axis (PCA) and a line drawn through the center of the femoral head and neck. While less common, the transepicondylar axis (TEA) has also been used to reference femoral neck anteversion. The purpose of this study was to compare femoral neck version of the PCA vs the TEA using computerized tomography (CT).

Methods

A total of 1507 femoral CTs were included. Precise bony landmarks were established: lateral epicondyle, medial epicondyle, posteromedial condyle, posterolateral condyle, center of the femoral neck, and center of the femoral head. Femoral version was calculated between the head and neck axis and either the PCA or TEA. Differences between sex and ethnicity were evaluated.

Results

The mean femoral anteversion was 12.7° ± 9.1° based on the PCA and 11.5° ± 7.9° based on the TEA (mean difference 1.2° ± 1.9°, P < .001). Males were less anteverted than females (9.8° ± 7.6° vs 13.5° ± 7.8°, P < .001). African Americans had less anteversion than other groups (8.1° ± 9.2° vs 11.5° ± 7.8°, P = .04), while Asians were more anteverted than other groups (12.1° ± 9.0° vs 11.2° ± 7.3°, P = .04). These values were referenced on the TEA.

Conclusions

In this series of over 1500 femoral CT scans, the mean difference between anteversion measurements referencing the PCA and TEA was 1.2°. Native femoral version varied widely between gender and ethnic groups. Extreme femoral version, defined as <0° or >30°, was present in 11.8% of patients referencing the PCA.

[Translated article] Clinical results of total hip arthroplasty assisted by robotic arm in Spain: Preliminary study

OBJECTIVES

Clinical, radiological and functional results of the first Spanish series of patients undergoing total hip arthroplasty assisted by Mako® (Stryker) robotic arm at the Hospital Clínico San Carlos (HCSC) in Madrid.

MATERIAL AND METHODS

Prospective and descriptive study analyzing the first 25 patients who underwent robotic-assisted THA at the HCSC, with a minimum follow-up of 4 months. Demographics, imaging studies (Mako® processing, Rx and CT), clinical parameters, functionality (modified Harris) and associated complications were evaluated.

RESULTS

Average age was 67.2 years (min 47, max 88), being 56% male population sample. 88% involves primary coxarthrosis, 4% post-traumatic coxarthrosis, 4% secondary avascular necrosis and 4% secondary femoroacetabular impingement. Average surgery time was 116.9min (min 92, max 150). The average time of the first five surgeries was 122.6min, and, regarding the last five interventions, it was 108.2min. Found medical intraoperative complications were four intraoperative markers loss. Average admission time was 4.4days (min 3, max 7), with an average postoperative haemoglobin decrease of 3.08±1.08g/dl, requiring a transfusion in 12% of the cases. Three medical complications have been registered in the meantime of the admission, with a relevant case of a confusional syndrome and a fall, which resulted in a non-displaced AG1 periprosthetic fracture. The analysis of the positioning of registered implants with Mako® system shows 40.55±1.53 acetabular inclination degrees and 12.2±3.6 acetabular anteversion degrees. The postoperative image study carried out on patients, are consistent with Mako® results, as it shows an acetabular inclination of 41.2±1.7 in Rx, as well as acetabular anteversion of 16±4.6 in CT. Hip length variance ranges depending on preoperative values of 3.91mm (SD: 3.9; min -12, max 3) to 1.29mm (SD: 1.96) after surgery registered with Mako®, with an increase of an average hip length of 5.64mm (SD: 3.35). Rx simple study results show a postoperative difference between both hips of 0.5±3.08mm, which is consistent with Mako® results. Native femoral offset was stable after surgery with a showing difference both pre and post operative of the intervened hip of 0.1mm (SD: 3.7), registered with Mako®. Preoperatory modified Harris punctuation was 41.6±13.3, improving to postoperative values of 74.6±9.7 after four months since the surgery. No complications were registered in immediate postoperative (4 months).

CONCLUSIONS

Total hip arthroplasty robot-assisted achieves an adequate precision and repeatability of the implant positioning and the postoperative hip dysmetry without showing an increase of associated complications to the technique applied. Surgery time, complications and functional results in a short-time period are similar to conventional techniques applied to great series previously published.

Clinical results of total hip arthroplasty assisted by robotic arm in Spain: Preliminary study

OBJECTIVES

Clinical, radiological and functional results of the first Spanish series of patients undergoing total hip arthroplasty assisted by Mako® (Stryker) robotic arm at the Hospital Clínico San Carlos (HCSC) in Madrid.

MATERIAL AND METHODS

Prospective and descriptive study analyzing the first 25 patients who underwent robotic-assisted THA at the HCSC, with a minimum follow-up of 4months. Demographics, imaging studies (Mako® processing, Rx and CT), clinical parameters, functionality (modified Harris) and associated complications were evaluated.

RESULTS

Average age was 67.2years (min 47, max 88), being 56% male population sample. 88% involves primary coxarthrosis, 4% post-traumatic coxarthrosis, 4% secondary avascular necrosis and 4% secondary femoroacetabular impingement. Average surgery time was 116.9min (min 92, max 150). The average time of the first five surgeries was 122.6min, and, regarding the last five interventions, it was 108.2min. Found medical intraoperative complications were four intraoperative markers loss. Average admission time was 4.4days (min 3, max 7), with an average postoperative hemoglobin decrease of 3.08±1.08g/dL, requiring a transfusion in 12% of the cases. Three medical complications have been registered in the meantime of the admission, with a relevant case of a confusional syndrome and a fall, which resulted in a non-displaced AG1 periprosthetic fracture. The analysis of the positioning of registered implants with Mako® system shows 40.55±1.53 acetabular inclination degrees and 12.2±3.6 acetabular anteversion degrees. The postoperative image study carried out on patients, are consistent with Mako® s results, as it shows an acetabular inclination of 41.2±1.7 in Rx, as well as acetabular anteversion of 16±4.6 in CT. Hip length variance ranges depending on preoperative values of 3.91mm (SD: 3.9; min -12, max 3) to 1.29mm (SD: 1.96) after surgery registered with Mako®, with an increase of an average hip length of 5.64mm (SD: 3.35). Rx simple study results show a postoperative difference between both hips of 0.5±3.08mm, which is consistent with Mako® results. Native femoral offset was stable after surgery with a showing difference both pre and post operative of the intervened hip of 0.1mm (SD: 3.7), registered with Mako®. Preoperatory modified Harris punctuation was 41.6±13.3, improving to postoperative values of 74.6±9.7 after four months since the surgery. No complications were registered in immediate postoperative (4month).

CONCLUSIONS

Total hip arthroplasty robot-assisted achieves an adequate precision and repeatability of the implant positioning and the postoperative hip dysmetry without showing an increase of associated complications to the technique applied. Surgery time, complications and functional results in a short-time period are similar to conventional techniques applied to great series previously published.

The Value of Computed Tomography Scan in Three-dimensional Planning and Intraoperative Navigation in Primary Total Hip Arthroplasty

Total hip arthroplasty (THA) is a frequently performed procedure; the objective is restoration of native hip biomechanics and achieving functional range of motion (ROM) through precise positioning of the prosthetic components. Advanced three-dimensional (3D) imaging and computed tomography (CT)-based navigation are valuable tools in both the preoperative planning and intraoperative execution. The aim of this study is to provide a thorough overview on the applications of CT scans in both the preoperative and intraoperative settings of primary THA. Preoperative planning using CT-based 3D imaging enables greater accuracy in prediction of implant sizes, leading to enhancement of surgical workflow with optimization of implant inventory. Surgeons can perform a more thorough assessment of posterior and anterior acetabular wall coverage, acetabular osteophytes, anatomical landmarks, and thus achieve more functional implant positioning. Intraoperative CT-based navigation can facilitate precise execution of the preoperative plan, to attain optimal positioning of the prosthetic components to avoid impingement. Medial reaming can be minimized preserving native bone stock, which can enable restoration of femoral, acetabular, and combined offsets. In addition, it is associated with greater accuracy in leg length adjustment, a critical factor in patients' postoperative satisfaction. Despite the higher costs and radiation exposure, which currently limits its widespread adoption, it offers many benefits, and the increasing interest in robotic surgery has facilitated its integration into routine practice. Conducting additional research on ultra-low-dose CT scans and examining the potential for translation of 3D imaging into improved clinical outcomes will be necessary to warrant its expanded application.

How the hip-spine relationship influences total hip arthroplasty

INTRODUCTION

Motion in the spine, pelvis and hips which make up the spinopelvic femoral complex (SPFC) implies mechanical relationships that help maintain trunk balance and optimize hip functionThe aim of this study was to understand the physiology of the SPFC and evaluate the dysfunctions of the SPFC and their implications for total hip arthroplasty considering the hip-spine relationship.

METHODS

A review of relevant and comprehensive studies on this subject is reported in order to highlight a pathophysiology that integrates the description of the evaluations of the spine-pelvic and hip parameters and recommendations for the kinematic planning of the THA procedure. The primary objective was to determine which type of hip-spine relationship has the highest risk for THA complications and to become proficient in selecting the priority surgical intervention when both the hip and spine are affected. Finally, this review attempted to assist hip surgeons with surgical technique, tools, implant selection, and goals of planning a THA that requires personalized kinematic alignment. Determine the influence of THA on these kinematics and the effect of stiffness of the lumbopelvic complex on the risk of THA failure.

RESULTS

When a person sits, the pelvis goes into retroversion and the acetabulum opens forward. This frees the femoral head and neck to allow hip flexion. The opposite - pelvic anteversion - occurs when a person stands. When pelvic mobility is limited, the hip must increase its range of motion to accommodate these posture changes. Disturbances in spinal and pelvic kinematics lead to abnormal hip function, which may contribute to complications following total hip arthroplasty (THA).

CONCLUSION

A precise evaluation of the parameters governing the SPFC must be taken into account in order to best optimize the placement and choice of THA implants.

LEVEL OF EVIDENCE

IV.

Superior outcomes of total hip arthroplasty without prior lumbar arthrodesis: a systematic review and meta-analysis

PURPOSE

The number of patients undergoing total hip arthroplasty (THA) surgery after previous lumbar arthrodesis (LA) is rising. Literature suggests that LA may significantly impact pelvic biomechanics and potentially compromise the success of prosthetic hip replacement. This study aims to evaluate complication rates, dislocation rates, and revision rates in patients with prior LA undergoing THA surgery compared to those undergoing THA surgery without prior LA.

METHODS

A systematic review and meta-analysis were conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A PICOS template was developed to ensure a structured approach. The search for relevant studies was performed across five databases, including Pubmed, Scopus, Embase, Medline, and Cochrane. The selected articles were evaluated based on the Levels of Evidence (LoE) criteria. The Coleman Methodology Score (mCMS) was employed to analyze the retrospective studies. This systematic review and meta-analysis were registered in the International Prospective Register of Systematic Reviews (PROSPERO). For the outcomes that allowed for a meta-analysis performed using R software, a p < 0.05 was considered statistically significant.

RESULTS

The final analysis included seventeen studies comprising a total of 3,139,164 cases of THA. Among these cases, 3,081,137 underwent THA surgery alone, while 58,027 patients underwent THA with a previous LA. The study investigated various factors, including dislocation rates, revision rates, and complication, as well as the surgical approach and type of implant used, for both the THA-only group and the group of patients who underwent THA with prior LA. The analysis revealed a statistically significant difference (p < 0.05) for all variables studied, favoring the group of patients who underwent THA alone without prior LA.

CONCLUSIONS

This systematic review and meta-analysis demonstrated a statistically significant superiority in all analyzed outcomes for patients who underwent THA-only without prior LA. Specifically, patients with isolated THA implants experienced significantly lower incidences of THA dislocation, wound complications, periprosthetic joint infection, revision, and mechanical complications.

LEVEL OF EVIDENCE

Level IV.

Optimization of Acetabular Cup Abduction by Adjusting Pelvic Pitch

Background

The purposes of this study were to determine the accuracy of our cup positioning method and to evaluate the dislocation rate after total hip arthroplasty (THA).

Methods

After positioning the patient in the lateral decubitus position on the operation table, an anteroposterior view of the hip was taken. The pelvic pitch was measured on the X-ray. A positive pitch was defined as the caudal rotation of the upper hemipelvis. Our target abduction of the cup was 43°. We used the cup holder to guesstimate the cup abduction. In a preliminary study, we found that the weight of the cup holder increased the pelvic pitch by 5°. Thus, the target abduction of the cup holder was calculated by a formula: 43° - pelvic pitch - 5°. During the cup insertion, the cup holder was anteverted to the calculated target according to the concept of combined anteversion. We evaluated 478 THAs (429 patients), which were done with the use of the method.

Results

The mean cup abduction was 43.9° (range, 32.0°-53.0°) and the mean error of cup abduction was 2.4° (standard deviation [SD], 2.0°; range, 0.0°-11.0°). The mean cup anteversion was 28.5° (range, 10.0°-42.0°) and the mean error of cup anteversion was 6.7° (SD, 5.2°; range, 0.0°-27.6°). Of all, 82.4% of the cups (394 / 478) were within the safe zone: 30°-50° abduction and 10°-35° anteversion. During 2- to 5-year follow-up, no hip dislocated.

Conclusions

Our adjusting method according to the pelvic pitch can be a reliable option for optimizing the cup abduction in THA.

Intraoperative Assessment of Stability in Total Hip Arthroplasty: A Novel Method Utilizing Implant Collinearity

Background

Hip dislocation remains a leading cause of revision following total hip arthroplasty, and intraoperative assessment of acetabular positioning can be difficult to perform. There are multiple clinical tests, as well as computer and robotic techniques, that aim to reduce dislocation rates after hip arthroplasty. These approaches aim to optimize the relationship between acetabular and femoral component positioning. It is hypothesized in this study that implant collinearity assessment intraoperatively can help determine appropriate acetabular component position. More specifically, implant collinearity, when achieved with a specific leg position, can reliably predict appropriate acetabular positioning.

Methods

A single-surgeon, single-centered study with 55 patients was undertaken between August 2017 and March 2020. Using preoperative imaging and computer simulation, data points were taken for 3 different acetabular configurations and comparing using 2 femoral positions. The angle differences from the collinear position (0 degrees) were compared between groups.

Results

A total of 55 patients' imaging was analyzed using 3 acetabular configurations and 2 femoral positions. The test leg position (30-degree flexion/30-degree internal rotation/10-degree adduction) was closer to collinearity than the control position (30-degree flexion/30-degree internal rotation/0-degree adduction) in all 3 acetabular configurations by a mean of 8 degrees (P < .001), 7 degrees (P < .001), and 4 degrees (P < .001), respectively.

Conclusions

The use of a 10-degree adducted position more reliably recreates implant collinearity when determining acetabular positioning during total hip arthroplasty. This intraoperative test adds another data point to assist the surgeon in achieving safe component positioning.

Variety of femoral anteversion and its measurement in cementless total hip arthroplasty: Does robotic technology improve accuracy?

BACKGROUND

High-performance total hip arthroplasty (THA) depends on the accurate position of components. However, femoral anteversion is variable, and current studies only used traditional instruments to evaluate it, such as protractor and spirit level with limited cases. This study aimed to identify the variability in the measured femoral native anteversion and intraoperative stem anteversion under different measurement methods, including intraoperative robotic method. We hypothesized that robotic technology was more accurate than traditional instruments for femoral anteversion evaluation.

METHODS

This study included 117 hips of patients who underwent robotic-assisted THA between November 2019 and March 2021. Preoperative native femoral anteversion was measured using a robotic system. Intraoperative femoral stem anteversion was evaluated visually, and then measured with a goniometer and a robotic system, respectively. Variability in the measured femoral native anteversion and intraoperative femoral stem anteversion was calculated and compared. Intraclass correlation coefficient (ICC) and Pearson correlation analysis were used to assess the consistency and correlation of anteversion of different measurements and postoperative CT-measured stem anteversion, respectively.

RESULTS

The result of measurement for preoperative native femoral anteversion was more variable than the intraoperative robotic-measured stem anteversion. Intraoperative robotic-measured stem version showed the highest correlation with postoperative CT measurement of stem version (r = 0.806, P < 0.001), while intraoperative surgeon estimation had the lowest correlation coefficient (r = 0.281, P = 0.025). As for the consistency with postoperative CT measurement of femoral stem anteversion, the intraoperative robotic-measured femoral stem version also had the highest value (ICC = 0.892, P < 0.001).

CONCLUSION

Native femoral anteversion was variable preoperatively. Using cementless stems, anteversion was also highly variable. Robotic assessment for stem anteversion during surgery was more consistent with the final position than the preoperative assessment and conventional intraoperative estimation.

Anatomical cup implantation assisted with dynamic 3D planning improves functional outcomes in primary total hip arthroplasty: A retrospective study

BACKGROUND

Anatomical cup implantation is a promising approach in primary total hip arthroplasty (THA) and improves functional outcomes.

OBJECTIVE

We aimed to evaluate the cup position and functional outcomes in primary THA with preoperative dynamic 3D planning.

METHODS

We retrospectively reviewed 54 hips in 48 patients who underwent primary THA with anatomical cup implantation (mean follow-up time: 52 months). Cup positions were evaluated based on patient-specific morphology, the acetabular fossa and the combined anteversion test. Functional outcomes were assessed after THA. The paired-sample t-test was performed for surgical and contralateral native hips among 42 patients who underwent unilateral THA.

RESULTS

Two hips suffered intraoperative trochanteric fracture, but no hip dislocations occurred. No patients reported groin or thigh pain, and all patients were capable of deep squatting and one-leg standing. The mean Harris hip score, WOMAC score, and physical SF-36 score were 94.46 ± 6.16, 10.41 ± 3.62, and 95.19 ± 8.74, respectively. Except for acetabular offset, THA restored biomechanics to those of contralateral native hip, including cup anteversion, abduction, femoral offset and acetabular height (P> 0.05).

CONCLUSION

This study provided evidence for the application of anatomical cup implantation assisted with dynamic 3D planning in primary THA, which restored morphology and improved functional outcomes.

Combined Anteversion Threshold to Avoid Anterior Dislocation in Primary Total Hip Arthroplasty Performed Through the Direct Anterior Approach

BACKGROUND

Component malposition in total hip arthroplasty (THA) can lead to dislocation, early implant failure, and revision surgery. As the surgical approach might affect the targeted combined anteversion (CA) of THA components, the present study aimed to evaluate the optimal CA threshold to avoid anterior dislocation in primary THA performed through a direct anterior approach (DAA).

METHODS

A total of 1,176 THAs in 1,147 consecutive patients (men: 593, women: 554) who had an average age of 63 years (range, 24 to 91) and a mean body mass index of 29 (range, 15 to 48) were identified. Medical records were reviewed for dislocation, whereas postoperative radiographs were assessed to measure the acetabular inclination and CA using a previously validated radiographic method.

RESULTS

An anterior dislocation occurred in 19 patients at an average of 40 days postoperatively. The average CA in patients who did and did not have a dislocation was 66 ± 8° and 45 ± 11°, respectively (P < .001). In 5 of 19 of the patients, a THA was performed for secondary osteoarthritis and 17 of 19 had a 28-mm femoral head. A CA ≥ 60° yielded a sensitivity of 93% and specificity of 90% for predicting an anterior dislocation in the present cohort. A CA ≥ 60° was associated with a significantly higher risk of anterior dislocation (odds ratio = 75.6; P < .001) compared to patients who had a CA<60 points.

CONCLUSION

The optimal CA to avoid anterior dislocations in THA performed through the DAA should be less than 60°.

LEVEL OF EVIDENCE

Cross-sectional study, Level III.

Cemented or uncemented fixation: Which allows a more acceptable prosthetic femoral version in total hip arthroplasty?

BACKGROUND

Three-dimensional computed-tomography (3D-CT) planning for primary Total Hip Arthroplasty (THA) typically uses the external femoral surface; as a result, it is difficult to predict the prosthetic femoral version (PFV) for uncemented femoral stems that press-fit to the internal surface of the bone. Cemented fixation allows the surgeon to adjust the version independent of the internal femoral anatomy. We aimed to better understand the effect of the fixation type on PFV.

METHODS

This was a case series study including a total of 95 consecutive patients (106 hips), who underwent uncemented (n = 81 hips) and cemented (n = 25 hips) primary THA using the posterior approach. The surgeon aimed for a PFV of 20°. Our primary objective was to compare PFV in both groups; our secondary objective was to evaluate the clinical outcomes.

RESULTS

The mean (± SD) PFV was 13° (± 9°) and 23° (± 8°) for the uncemented and cemented THA groups (P < 0.001), respectively. In the uncemented THA group, 36% of the patients had a PFV of < 10°. In the cemented THA group, this clinically important threshold dropped to 8%. Similarly, the Bland-Altman (BA) plots showed wider 95% limits of agreement for the uncemented group. Satisfactory clinical outcomes were recorded.

CONCLUSION

We found that the PFV was more clinically acceptable, for the posterior surgical approach, in the cemented group when compared to the uncemented group. Both THA groups reported high variability indicating the need to develop surgical tools to guide the PFV closer to the surgical target.

Early outcomes of total hip arthroplasty using point-of-care manufactured patient-specific instruments: a single university hospital's initial experience

BACKGROUND

The use of 3D-printed Patient-Specific Instruments (PSI) has been investigated to enhance the postoperative functional results in total hip arthroplasty (THA) and has been recognized as an innovative approach for the optimal alignment of hip implant components. Point-of-care production is gradually becoming the norm for PSI manufacturing. The purpose of this article is to assess the accuracy and safety of PSI for total hip arthroplasty performed at the point-of-care in Vietnam.

METHODS

34 THA cases were assessed in this prospective study. A template for the size and orientation of the implant and the design of the PSI was generated using data from preoperative 3D computed tomography (CT) scanning of the lower limb. The principal surgeon determined the implants' position and PSI design directly using the software. The PSI is then produced using a 3D-compatible resin printer in our manufacturing hospital. The PSI, consisting of an acetabulum and a femoral component placed press-fit on the bony surface, guided surgeons to precisely ream the acetabulum and cut the femoral neck according to the pre-planned plane. Postoperative CT scanning was obtained and superimposed onto the 3D model of the implant to evaluate the accuracy of the procedure by comparing the orientation values of the cup and the alignment of the stem between the planned and the actual results. Intra- and postoperative clinical parameters of surgery, including surgical time, intra-operative blood loss, complications, and the first ambulation, were also recorded to evaluate the safety of the surgery.

RESULTS

The preparation for PSI required an average of 3 days. 94% of cup size and 91% of stem size were correctly selected. The mean values of postoperative inclination and anteversion were 44.2° ± 4.1° and 19.2° ± 5.6°, respectively. 64.7% of cases deviated from planned within the ± 50 range and 94.1% within the ± 10° range. There was no significant statistical difference between the planned and the achieved values of stem anteversion, osteotomy height, and leg length discrepancy (p > 0.05). The average surgical time was 82.5° ± 10.8 min, and the intraoperative blood loss was estimated at 317.7° ± 57.6 ml. 64.7% of patients could walk on the day of surgery. There were no complications reported.

CONCLUSIONS

The point-of-care manufactured PSI is a useful solution for improving the accuracy of total hip arthroplasty surgery, especially in restoring implant orientation and reducing leg length discrepancy. However, long-term clinical follow-up evaluation is needed to confirm the efficacy and safety of this approach.

Accuracy and safety of a new robotic arm for both femoral and acetabular side in total hip arthroplasty: a cadaveric study

BACKGROUND

To investigate the accuracy and safety of a newly constructed robotic arm which can cover the whole process of THA, we performed a series of robot-assisted total hip replacement on the cadaver.

METHODS

Fifteen frozen cadaveric specimens (30 hips) were used for this study. In this investigation, united hip system and Longwell robotic-assisted system were used. The entire lower limb was CT scanned prior to surgery. The 3D model was produced based on CT data; the site of the prosthesis, including acetabular anteversion, inclination angle, and the position of femoral prosthesis, was planned. With the assistance of a robotic arm, the surgeon changed the parameters based on the preoperative plan and the actual condition during surgery, and completed the whole procedure. Following surgery, we measured the acetabular anteversion angle, acetabular inclination angle, femur anteversion angle, combined anteversion angle, stem angulation, and canal fill ratio.

RESULTS

The parameters proved that the acetabular anteversion angle was 16.85 ± 3.00°, the acetabular inclination angle was 40.38 ± 5.37°, femur anteversion angle was 15.90 ± 9.01°, combined anteversion angle was 32.75 ± 9.03°, stem angulation was 1.84 ± 0.99°, and leg length discrepancy was 2.47 ± 1.43 mm. The canal fill ratio (CFR) of femoral prosthesis of osteotomy line in sagittal section is 99.72 ± 1.54% and in coronal section is 62.94 ± 8.91%; below osteotomy line 2.5 cm in sagittal section is 100.00% and in coronal section is 81.48 ± 12.94%; below osteotomy line 7.5 cm in sagittal section is 59.51 ± 12.94% and in coronal section is 89.79 ± 11.13%; femoral shaft isthmus in sagittal section is 56.41 ± 13.80% and in coronal section is 84.95 ± 15.17%.

CONCLUSION

The accuracy and safety of this novel robotic arm are suitable for preparing both the acetabular and femoral sides, providing evidence for clinical trial.

A review of robotic-assisted total hip arthroplasty

Total hip arthroplasty (THA) is a successful surgical method for hip replacement but still poses challenges and risks. Robotic-assisted THA (rTHA) using new generation robotic systems has emerged to improve surgical precision and outcomes. The purpose of this paper is to review the literature on rTHA, with a focus on its advantages, such as individualized preoperative planning, intraoperative assistance, and improved accuracy in implantation, especially in complex cases. Additionally, it aims to explore the disadvantages associated with the use of rTHA, including high costs, the learning curve, and prolonged operation time compared to manual THA (mTHA), which are critical drawbacks that require careful consideration and efforts for minimization. Some financial analyses suggest that rTHA may offer cost-effectiveness and reduced postoperative costs compared to mTHA. While technological advancements are expected to reduce technical complications, there are still debates surrounding long-term outcomes. Practical limitations, such as limited availability and accessibility, also warrant attention. Although the development of rTHA shows promise, it is still in its early stages, necessitating critical evaluation and further research to ensure optimal patient benefits.

"Single-use peripheral" vs "conventional" reaming in total hip arthroplasty: how to respect native centre of rotation and acetabular offset? A CT study

PURPOSE

The respect of native hip offset represents a mainstay for satisfying results in total hip arthroplasty (THA). Historically, a great interest has been focused on restoration of femoral offset, while only in recent years, acetabular offset (AO) has been considered. The purpose of the current study was to compare the "single-use peripheral" reaming technique with the "conventional" one for the maintenance of the native COR of the hip and AO in patients undergoing to primary THA.

METHODS

Eighty patients affected from primary hip osteoarthritis were prospectively enrolled in the study and were divided in two groups (Group A "single-use peripheral" and Group B "conventional" reaming technique). Pre- and post-operatively, AO, acetabular floor distance (AFd) and acetabular version (AV) were assessed through a CT scan. A comparison between groups for the radiological parameters, surgical time and complications was performed.

RESULTS

The demographic data were similar in both groups. The complications rate and the AV did not differ statistically between groups. Group A presented a statistically significant shorter surgical time and lower variation between pre- and post-operative AO and AFd. Statistical significance was defined as p < 0.05.

CONCLUSIONS

The "single-use peripheral" reaming technique demonstrated to be more reliable in reproducing the native COR and AO of patients undergoing to primary THA than the "conventional" one. The operative time was significantly reduced, and it may lead to a reduction in the infection risk even though it was not observed in the current study. Further research could be useful to validate such findings and to assess clinical impact and long-term survival of the implant.

Increased Cup Anteversion May Not Prevent Posterior Dislocation in Patients With Abnormal Spinopelvic Characteristics in Total Hip Arthroplasty

Background

The aims of this study were to (1) assess the degree of variation in acetabular component placement and combined anteversion in a large cohort of dislocating total hip arthroplasties; (2) assess the spinopelvic characteristics of the cohort; and (3) examine the association between cup anteversion and reported direction of instability.

Methods

A commercial database of 245 dislocating total hip arthroplasties referred for postoperative computed tomography and functional radiographic imaging and analysis were reviewed. Spinopelvic parameters and cup and stem positions were measured in the supine, standing, flex-seated, and anterior pelvic plane (APP) positions. Spinopelvic characteristics were stratified by high, neutral, and low cup anteversion using thresholds of >35° and <15° anteversion in standing, respectively.

Results

In the dislocation cohort, 62%, 45%, and 42% of cups were within the safe zone in supine, standing, and the APP, respectively (P < .001). Patients with high vs neutral or low cup anteversion had significantly stiffer spines, more posterior pelvic tilt in standing, greater changes in pelvic tilt, and higher sagittal imbalance. Of the 45 patients with high cup anteversion and reported instability direction, 60% and 40% were reported to have posterior and anterior instability, respectively, with no differences in spinopelvic characteristics.

Conclusions

In this dislocating cohort, there is a decreased percentage of cups within the safe zone in the APP and standing position compared to the supine reference. In addition, we found that patients having poor spinopelvic characteristics and high cup anteversion can still dislocate, suggesting that adjusting cup anteversion alone may not be sufficient for preventing instability.

Defining the optimal position of the lipped liner in combination with cup orientation and stem version

Aims

The aim of this study was to identify the optimal lip position for total hip arthroplasties (THAs) using a lipped liner. There is a lack of consensus on the optimal position, with substantial variability in surgeon practice.

Methods

A model of a THA was developed using a 20° lipped liner. Kinematic analyses included a physiological range of motion (ROM) analysis and a provocative dislocation manoeuvre analysis. ROM prior to impingement was calculated and, in impingement scenarios, the travel distance prior to dislocation was assessed. The combinations analyzed included nine cup positions (inclination 30-40-50°, anteversion 5-15-25°), three stem positions (anteversion 0-15-30°), and five lip orientations (right hip 7 to 11 o'clock).

Results

The position of the lip changes the ROM prior to impingement, with certain combinations leading to impingement within the physiological ROM. Inferior lip positions (7 to 8 o'clock) performed best with cup inclinations of 30° and 40°. Superior lip positions performed best with cup inclination of 50°. When impingement occurs in the plane of the lip, the lip increases the travel distance prior to dislocation. Inferior lip positions led to the largest increase in jump distance in a posterior dislocation provocation manoeuvre.

Conclusion

The lip orientation that provides optimal physiological ROM depends on the orientation of the cup and stem. For a THA with stem anteversion 15°, cup inclination 40°, and cup anteversion 15°, the optimal lip position was posterior-inferior (8 o'clock). Maximizing jump distance prior to dislocation while preventing impingement in the opposite direction is possible with appropriate lip positioning.

A novel method for evaluating combined component anteversion in total hip arthroplasty on cross-table lateral hip radiographs

INTRODUCTION

Accurate measurement of combined component anteversion (CA) is important in evaluating the radiographic outcomes following total hip arthroplasty (THA). The aim of the present study was to evaluate the accuracy and reliability of a novel radiographic method in estimating CA in THA.

MATERIALS AND METHODS

The radiographs and computer tomography of patients who underwent a primary THA were retrospectively reviewed, to measure the radiographic CA (CAr), defined as the angle between a line connecting the center of the femoral head to the most anterior rim of the acetabular cup and a line connecting the center of the femoral head to the base of the femoral head to allow a comparison with the CA measured on the CT (CACT). Subsequently, a computational simulation was performed to evaluate the effect of cup anteversion, inclination, stem anteversion, and leg rotation on the CAr and develop a formula that would correct the CAr according to the acetabular cup inclination based on the best-fit equation.

RESULTS

In the retrospective analysis of 154 THA, the average CAr_cor, and CACT were 53 ± 11° and 54 ± 11° (p > 0.05), respectively. A strong correlation was found between CAr and CACT (r = 0.96, p < 0.001), with an average bias of - 0.5° between CAr_cor and CACT. In the computational simulation, the CAr was strongly affected by the cup anteversion, inclination, stem anteversion, and leg rotation. The formula to convert the CAr to CA_cor was: CA-cor = 1.3*Car - (17* In (Cup Inclination) - 31.

CONCLUSION

The combined anteversion measurement of THA components on the lateral hip radiograph is accurate and reliable, implying that it could be routinely used postoperatively but also in patients with persistent complaints following a THA.

LEVEL OF EVIDENCE

Cross-sectional study, Level III.

Contralateral Hip Abductor Muscle Strength Associated with Comfort of Getting into and out of the Car after Total Hip Arthroplasty

There are no studies that have investigated the characteristics of car use across THA patients, including those who do not drive. This study aimed to evaluate, in THA patients, (1) postoperative car usage, (2) comfort while entering and exiting a car, and (3) whether lower limb muscle strength affects action comfort. One hundred seventy-two post-THA patients completed the questionnaire in 2020, along with assessments of hip abductor and knee extensor muscle strength before surgery and at discharge. Patients whose overall comfort level was judged as comfortable were defined as the comfort group; others were placed in the discomfort group. Of the 172 patients, 161 reported car usage at a mean of 5.6 years after THA. Of these, 114 and 47 patients were placed in the comfort and discomfort groups, respectively. Patients in the discomfort group were three times more likely to experience discomfort using the contralateral side door than the surgical side door, and about twice as many patients experienced discomfort when entering as when exiting. Lower preoperative contralateral hip abductor muscle strength was the only independent predictor for discomfort. The take-home messages were that prevention of contralateral-side weakness may improve comfort during the action after THA.

Can version of the proximal femur be used for CT planning uncemented femoral stems?

Three-Dimensional Computed Tomography (3D-CT) planning can predict the prosthetic femoral size in uncemented primary Total Hip Arthroplasty (THA). Correct sizing usually results in optimal varus/valgus femoral alignment; however, its effect on the Prosthetic Femoral Version (PFV) is poorly understood. Most 3D-CT planning systems use Native Femoral Version (NFV) to plan PFV. We aimed to assess the relationship between PFV and NFV in primary uncemented THA using 3D-CT analysis. Pre- and post-operative CT data was retrospectively collected from 73 patients (81 hips) undergoing primary uncemented THA with a straight-tapered stem. 3D-CT models were used to measure PFV and NFV. The clinical outcomes were evaluated. The discrepancy between PFV and NFV was low (<5°) in 43%, moderate (5-10°) in 40%, high (10-15°) in 11% and very high (>15°) in 6% of the cases. We found that NFV is not a useable guide for planning PFV. The 95% limits of agreement were both high at 17° and 15°, respectively. Satisfactory clinical outcomes were recorded. The discrepancy was large enough to recommend against the use of NFV for planning PFV when using straight-tapered uncemented stems. Further work should focus on the internal bony anatomy and the influence of stem design when planning uncemented femoral stems.

Effect of Total Hip Arthroplasty on Ipsilateral Lower Limb Alignment and Knee Joint Space Width: Minimum 5-Year Follow-up

BACKGROUND

This study aimed to 1) assess the effect of total hip arthroplasty (THA) on coronal limb alignment, namely, the hip-knee-ankle angle (HKA), 2) identify factors that determine changes in the HKA, and 3) determine whether alignment changes influence the knee joint space width.

METHODS

We retrospectively evaluated 266 limbs of patients who underwent THA. Three types of prostheses with neck shaft angles (NSAs) of 132°, 135°, and 138° were used. Several radiographic parameters were measured in the preoperative and final radiographs (at least 5 years after THA). A paired t-test was used to confirm the effect of THA on HKA change. Multiple regression analysis was performed to identify radiographic parameters related to HKA changes following THA and changes in knee joint space width. Subgroup analyses were performed to reveal the effect of NSA change on the HKA change, and the proportion of total knee arthroplasty usage and changes in radiographic parameters between maintained joint space and narrowed joint space groups were compared.

RESULTS

The preoperative mean HKA was 1.4° varus and increased to 2.7° varus after THA. This change was related to changes in the NSA, lateral distal femoral angle, and femoral bowing angle. In particular, in the group with a decrease in NSA of > 5°, the preoperative mean HKA was largely changed from 1.4° varus to 4.6° varus after THA. The prostheses with NSA of 132° and 135° also led to greater varus HKA changes than those with an NSA of 138°. Narrowing of the medial knee joint space was related to changes in the varus direction of the HKA, decrease in NSA, increase in femoral offset.

CONCLUSION

A large reduction in NSA can lead to considerable varus limb alignment after THA, which can have adverse effects on the medial compartment of the ipsilateral knee.

A Comparison of Radiographic Outcomes after Total Hip Arthroplasty between the Direct Lateral Approach and Posterior Lateral Approach with EOS 2D/3D X-Ray Imaging System

OBJECTIVE

The classical approaches for total hip arthroplasty (THA) are the direct lateral approach (DLA) and posterior lateral approach (PLA). There are few studies comparing implant orientation with these two approaches, and the impact of surgical approaches on implant orientation remains controversial. With the rise of the EOS imaging system, we aimed to use it to identify the differences between and factors associated with implant orientation after THA using DLA and PLA.

METHODS

In our department from January 2019 to December 2021, 321 primary unilateral THAs that used PLA and DLA were enrolled. A total of 201 patients who received PLA and 120 patients who received DLA were included in this study. Two blinded observers measured each case using EOS imaging data. Postoperative imaging metrics and other relevant influencing factors of the two surgical approaches were compared. Postoperative imaging metrics, including the anteversion and inclination of the cup, anteversion of the stem, and combined anteversion were measured based on EOS. Other relevant influencing factors included age, approach, gender, laterality, BMI, anterior pelvic plane inclination, femoral head diameter, femoral offset, lateral pelvic tilt, pelvic incidence, pelvis axial rotation, sacral slope, sagittal pelvic tilt, and surgery time. Multiple linear regression analyses were performed to identify the predictors of acceptability for each imaging data point.

RESULTS

No dislocation was found in the 321 patients who underwent primary THA during this period. The mean anteversion and combined anteversion of the cups using the DLA were 21.33° ± 17.31° (-51.7°-60.8°) and 33.71° ± 20.85° (-38.8°-77.6°) and PLA were 25.34° ± 12.76° (-5.5°-57.0°) and 42.37° ± 18.85° (-8.7°-84.7°), respectively. The DLA group had smaller anteversion (p = 0.038) and combined anteversion (p < 0.001). We found that surgical approach (p < 0.05), anterior pelvic plane inclination (p < 0.001), gender (p < 0.001), and femoral head diameter (p < 0.001) were important factors affecting acetabular cup anteversion (R2  = 0.375) and combined anteversion (R2  = 0.525).

CONCLUSIONS

In total hip arthroplasty, different prosthesis installation directions should be made according to different surgical approaches. Compared with the direct lateral approach, the acetabular anteversion can be intentionally enlarged when using the posterolateral approach. Surgical approach, anterior pelvic plane inclination (APPI), gender, and femoral head diameter were significant predictors of prosthesis orientation. The anterior pelvic plane inclination may be a useful standard for assessing the position of the prosthesis using EOS.

Guiding prosthetic femoral version using 3D-printed patient-specific instrumentation (PSI): a pilot study

BACKGROUND

Implantation of the femoral component with suboptimal version is associated with instability of the reconstructed hip joint. High variability of Prosthetic Femoral Version (PFV) has been reported in primary Total Hip Arthroplasty (THA). Three-dimensional (3D) Patient-Specific Instrumentation (PSI) has been recently developed and may assist in delivering a PFV within the intended range. We performed a pilot study to better understand whether the intra-operative use of a novel PSI guide, designed to deliver a PFV of 20°, results in the target range of PFV in primary cemented THA.

METHODS

We analysed post-operative Computed-Tomography (CT) data of two groups of patients who underwent primary cemented THA through posterior approach; 1. A group of 11 patients (11 hips) for which the surgeon used an intra-operative 3D-printed stem positioning guide (experimental) 2. A group of 24 patients (25 hips) for which the surgeon did not use the guide (control). The surgeon aimed for a PFV of 20°, and therefore the guide was designed to indicate the angle at which the stem was positioned intra-operatively. PFV angles were measured using the post-operative 3D-CT models of the proximal femurs and prosthetic components in both groups. Our primary objective was to compare the PFV in both groups. Our secondary objective was to evaluate the clinical outcome.

RESULTS

Mean (± SD) values for the PFV was 21.3° (± 4.6°) and 24.6° (± 8.2°) for the experimental and control groups respectively. In the control group, 20% of the patients reported a PFV outside the intended range of 10° to 30° anteversion. In the experimental group, this percentage dropped to 0%. Satisfactory clinical outcome was recorded in both groups.

CONCLUSION

The intra-operative use of a PSI PFV guide helped the surgeon avoid suboptimal PFV in primary cemented THA. Further studies are needed to evaluate if the PSI guide directly contributes to a better clinical outcome.

Precise acetabular positioning, discrepancy in leg length, and hip offset using a new seven-axis robot-assisted total hip arthroplasty system requires no learning curve: a retrospective study

Objective

The purpose of the present study was to determine the learning curve for a novel seven-axis robot-assisted total hip arthroplasty (RA-THA) system, and to explore whether it was able to provide greater accuracy in acetabular cup positioning, superior leg length discrepancy (LLD), and hip offset than conventional methods.

Methods

A total of 160 patients in which unilateral THA was performed in the second affiliated Hospital of Xi'an Jiaotong University from July 2021 to September 2022 were studied. The first 80 patients underwent robot-assisted THA, while conventional THA was performed on the subsequent 80 by the same team of experienced surgeons. The learning curve for the RA-THA system was evaluated using cumulative sum (CUSUM) analysis. The demographic data, preoperative clinical data, duration of surgery, postoperative Harris hip score (HHS) and postoperative radiographic data from patients that had conventional THA were compared.

Results

The 80 patients who underwent primary unilateral RA-THA comprised 42 males and 38 females and were followed up for 12 weeks. Using analysis by CUSUM, the learning curve of the RA-THA system could be divided into learning and proficiency phases, the former of which consisted of the first 17 cases. There was no significant difference between the learning and proficiency phases in terms of LLD, hip offset, or accuracy of acetabular prosthesis position in the RA-THA groups. The proportion of acetabular prostheses located in the Lewinnek safe zone was 90.5% in the proficiency group and 77.5% in the conventional group, respectively, a difference that was statistically significant (P < 0.05). The absolute error between target angle and postoperative measured angle of anteversion was statistically significant in the proficiency group and the conventional group((P < 0.05). Postoperative acetabular anteversion and LLD were 19.96 ± 5.68° and 6.00 (5.00) mm in the proficiency group, respectively, and 17.84 ± 6.81° and 8.09 (4.33) mm using conventional surgery, respectively (anteversion: P = 0.049; LLD: P < 0.001).

Conclusions

The surgical team required a learning curve of 17 cases using the RA-THA system to become proficient. There was no learning curve for other parameters, namely LLD, hip offset, or accuracy of acetabular prosthesis positioning. During the proficiency phase, the RA system was superior to conventional THA for control of leg length and accuracy of acetabular cup placement.

Ten to 13-Year Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty in Patients Less Than 30 Years Old

BACKGROUND

We previously reported mid-term results of total hip arthroplasty (THA) using Delta ceramic-on-ceramic (CoC) bearings in 72 patients (86 hips) who were <30 years old. Noise was noted in 8 (9.3%) of the hips, no osteolysis or loosening was detected, and no patient required reoperation. The purpose of this study was to assess clinical and radiographic outcomes, complications, and survivorship at >10 years after THA using Delta CoC bearings in patients who were <30 years old.

METHODS

Cementless THA with a Delta CoC bearing was performed between March 2008 and January 2012 in 91 hips of 76 patients who were <30 years old. Eighty-five hips in 71 patients (44 men and 27 women) with a mean age of 25.9 years (range, 16 to 29 years) at surgery were followed for a mean of 10.9 years (range, 10 to 13 years).

RESULTS

No ceramic bearings fractured. The incidence of squeaking increased to 5.9% (5 of 85), but the squeaking was not reproducible within individual patients. Periprosthetic osteolysis developed in 3 hips (3 patients): around the stem in 2 and around the metal shell in 1. The stem in 1 hip underwent revision because of a Vancouver type-B2 periprosthetic femoral fracture. One patient with systemic lupus erythematosus underwent irrigation and debridement for periprosthetic joint infection. Survivorship free of reoperation for any reason was 92.4% (95% confidence interval, 82.4% to 100%) at 13 years.

CONCLUSIONS

The long-term results and survivorship of Delta CoC THA in patients <30 years old were favorable.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

A comparison of accuracy and safety between stem-first and cup-first total hip arthroplasty: a prospective randomised controlled trial

BACKGROUND

The combined anteversion theory to prevent impingement in total hip arthroplasty (THA) has been proposed. However, because stem-anteversion is influenced by the native femoral anteversion and the stem flexion/extension angle, it is often difficult to adjust stem anteversion during surgery. Therefore, the stem-first (combined anteversion) technique may be useful to adjust and achieve appropriate cup anteversion during surgery with respect to the implanted stem anteversion angle. However, the technique may adversely affect cup or stem angle accuracy and result in intra-operative bleeding, post-operative adverse events, and prolonged operative time. It is inconclusive whether either the stem-first or cup-first technique is safe or accurate. Therefore, this study assessed the accuracy and safety of stem-first THA compared to those of cup-first THA.

MATERIALS AND METHODS

This prospective randomised controlled trial analysed 114 patients who were randomly divided into 2 groups (stem-first group: n = 57, cup-first group (control group): n = 57). Primary outcomes included cup and stem angle, the discrepancies from the targeted angle and combined anteversion (evaluated via CT at 3 months postoperatively). Secondary outcomes included intraoperative blood loss, operative time, WOMAC, and adverse events.

RESULTS

There were no significant differences in age, gender, BMI or in the primary and secondary outcomes between the 2 groups.

CONCLUSIONS

Performing stem-first in THA did not adversely affect cup and stem angle accuracy, or result in intraoperative bleeding, prolongation of operative time, or postoperative adverse events. Thus, performing stem-first may be advantageous for achieving combined anteversion theory.

TRIAL REGISTRATION

University Hospital Medical Information Network (UMIN) registration number UMIN000025189.

Effects of changes in whole-body alignment on ipsilateral knee pain after total hip arthroplasty

BACKGROUND

Total hip arthroplasty decreases hip pain and often reduces knee pain in patients with hip osteoarthritis. Whole-body alignment may be associated with knee pain, but to our knowledge this relationship has not been previously investigated. The purpose of this study was to investigate the effect of changes in whole-body alignment on ipsilateral knee pain in patients after total hip arthroplasty.

METHODS

In total, 94 patients with unilateral hip osteoarthritis who underwent total hip arthroplasty were enrolled in this study. A visual analog scale (VAS) was used to investigate perioperative knee pain. An EOS 2D/3D X-ray system was used to quantify the whole-body alignment of the spine, pelvis, and lower extremities in the standing position. The relationship between perioperative changes in knee pain and whole-body alignment was investigated.

RESULTS

Among 61 patients who had preoperative ipsilateral knee pain, pain resolved in 30 (50%) and persisted in 31 (50%) after surgery. In these patients, average ipsilateral knee pain decreased significantly after surgery, from 41 mm to 14 mm on the VAS (P < 0.01). Preoperative knee pain was correlated with femorotibial rotation, and postoperative knee pain was correlated with K-L grade, preoperative knee pain visualized analog scale, and preoperative sagittal vertical axis. Multiple linear regression identified preoperative sagittal vertical axis as significantly associated with residual postoperative ipsilateral knee pain.

CONCLUSIONS

Ipsilateral knee pain decreased in half of patients after total hip arthroplasty. Patients with a considerable forward-bent posture may have residual ipsilateral knee pain after total hip arthroplasty.

The association of postoperative global femoral offset with total hip arthroplasty outcomes

Global femoral offset (GFO) and femoral offset (FO) reportedly affect outcomes following total hip arthroplasty (THA). However, FO assessed using plain radiography is affected by internal and external rotations of the hip joint. We investigated the relationship between leg length discrepancy and Harris hip score (HHS), and their influence on acetabular offset (AO), FO, GFO, anterior femoral offset, and outcomes after THA. We retrospectively evaluated 140 patients with hip osteoarthritis who underwent THA. A three-dimensional (3D) pelvis and femur model created from computed tomography (data using ZedHip software was used to investigate these parameters. The modified (m)HHS scores were significantly improved from 49.0 to 88.8 in total mHHS, 20.0-44.5 in pain, and 28.9-44.4 points in function. Significant correlations were found between the differences in AO, FO, GFO, and pain score in binominal, with maximum values of - 1.24, + 1.54, and + 0.90 mm/100 cm body height, respectively. The maximum value of GFO and mHHS in binominal was + 1.17 mm/100 cm body height (BH). The optimal range of difference of GFO was - 1.75 to 4.09 mm/100 cm BH. This is the first report using a 3D method for assessing FO. Preoperative planning using the system could improve postoperative function.

Achieving Target Cemented Femoral Stem Anteversion Using a 3-Dimensional Model

Background

Total hip arthroplasty aims to provide patients with a pain-free and stable hip joint through optimization of biomechanics such as femoral anteversion. There are studies evaluating the limits of cementless stem version, however, none assessing the range of version achieved by a cemented collarless stem. A computed tomography (CT)-based study was performed, utilizing a contemporary robotic planning platform to assess the amount of rotation afforded by a cemented collarless stem, whilst maintaining native biomechanics.

Methods

The study utilized 36 cadaveric hips. All had CT scans of the pelvis and hip joints. The CT scans were then loaded into a contemporary robotic planning platform. A stem that restored the patients native femoral offset was selected and positioned in the virtual femur. The stem was rotated while checking for cortical contact at the level of the neck cut. Cortical contact was regarded as the rotation limit, assessed in both anteversion and retroversion. Target range for stem anteversion was 10°-20°. Failure to achieve target version triggered a sequence of adjustments to simulate surgical decisions.

Results

Native femoral offset and target version range was obtained in 29 of 36 (80.5%) cases. Following an adjustment sequence, 4 further stems achieved target anteversion with a compromise in offset of 2.3 mm. Overall 33 of 36 (91.7%) stems achieved the target anteversion range of 10°-20°.

Conclusions

Target femoral stem anteversion can be achieved using a cemented, collarless stem in a CT-based 3-dimensional model in 80.5% of hips. With a small compromise in offset (mean 2.3 mm), this can be increased to 91.7%.

Effectiveness and Accuracy of a Patient-Specific Instrumentation System for Total Hip Arthroplasty

OBJECTIVE

Traditional total hip arthroplasty (THA) is often performed by visual inspection due to the lack of reliable reference, which results in inappropriate position of prosthesis and poor outcomes. This study attempts to introduce a novel patient-specific instrumentation (PSI) system and assess its effectiveness and accuracy compared with freehand operation and robot system through bone model experiments.

METHODS

Equally divide 30 sawbone models into the freehand group, PSI group, and robot group. Ten sets of prosthesis parameters were randomly generated as planning, and the three groups underwent simulated THA depending on these parameters. After the placement of the femoral prosthesis, the acetabular anteversion plan was adjusted in the PSI and robot groups so that the combined anteversion was maintained before and after adjustment. After the surgery, the actual prosthesis parameters of all bone models were measured and analyzed statistically.

RESULTS

No statistically significant difference was found in femoral anteversion error among the three groups (p = 0.951). The errors of acetabular cup anteversion, acetabular cup abduction, and combined anteversion in PSI group were 3.92° (2.94°, 4.62°), 5.65° (4.63°, 6.70°), and 3.93° (2.94°, 4.62°), respectively, which were significantly smaller than those in the freehand group [11.84° (9.92°, 13.87°), 13.54° (9.81°, 15.21°), 16.04° (8.18°, 19.25°), respectively, p < 0.05], but significantly larger than those in the robot group [1.34° (0.98°, 1.70°), 1.80° (1°, 2.02°), 1.34° (0.98°, 1.70°), respectively, p < 0.05].

CONCLUSION

Compared with the traditional freehand operation, the patient-specific instrumentation system is feasible in total hip arthroplasty because it improves the accuracy of prosthesis placement. In addition, the rapid measurement of intraoperative femoral prosthesis parameters can help surgeons optimize preoperative planning.

A 10- to 12-year follow-up study of delta ceramic-on-ceramic total hip arthroplasty

BACKGROUND

We previously reported five-to-seven-year results of total hip arthroplasty (THA) with the use of delta ceramic-on-ceramic (CoC) bearing. We conducted an extension study with a CT scan at a minimum of 10 years after surgery.

METHODS

From March 2009 to March 2011, 273 patients (310 hips) received cementless THA with delta CoC bearing, porous-coated cup and hydroxyapatite-coated stem. In this extended study, 252 patients (144 men and 108 women) (288 hips) with a mean age of 49.7 years (16-83) at surgery were followed for a mean of 10.4 years (10-12) with CT scans in 133 hips (46.2%, 133/288). Clinical and radiographic evaluations were made at each follow-up and Kaplan-Meier survival analysis was performed with revision and reoperation as endpoints.

RESULTS

There were no more ceramic fractures. Compared to mid-term results, the incidence of squeaking and RLLs increased to 3.1% (9/288) and 19.4% (56/288), respectively. The RLL progressed to focal osteolysis in 3 hips (5.4%, 3/56). No hip had detectable wear or prosthetic loosening. Two hips were reoperated due to periprosthetic joint infection and periprosthetic femoral fracture in each. The survivorship decreased to 98.3% (96.7-99.9%) at 12 years.

CONCLUSION

During the extended follow-up, no additional ceramic fracture occurred, and the incidence of squeak increased by 0.7%. The long-term survivorship of Delta CoC THA was encouraging. However, focal osteolysis occurred around the hydroxyapatite-coated stem in 1% (3/288).

LEVEL OF EVIDENCE

II (Prospective cohort study).

Validating the accuracy of a novel virtual reality platform for determining implant orientation in simulated primary total hip replacement

Introduction

Accurate acetabular cup and femoral stem component orientation are critical for optimising patient outcomes, reducing complications and increasing component longevity following total hip replacement (THR). This study aimed to determine the accuracy of a novel virtual reality (VR) platform in assessing component orientation in a simulated THR model.

Methods

The VR platform (HTC Vive Pro® system hardware) was compared against the validated Vicon® optical motion capture (MoCap) system. An acetabular cup and femoral stem were manually implanted across a range of orientations into pelvic and femur sawbones, respectively. Simultaneous readings of the acetabular cup operative anteversion (OA) and inclination (OI) and femoral stem alignment (FSA) and neck anteversion (FNA) were obtained from the VR and MoCap systems. Statistical analysis was performed using Pearson product-moment correlation coefficient (PPMCC) (Pearson’s r) and linear regression (R²).

Results

A total of 55 readings were obtained for the acetabular cup and 68 for the femoral stem model. The mean average differences in OA, OI, FSA and FNA between the systems were 3.44°, −0.01°, 0.01° and −0.04°, respectively. Strong positive correlations were demonstrated between both systems in OA, OI, FSA and FNA, with Pearson’s r = 0.92, 0.94, 0.99 and 0.99, and adjusted R² = 0.82, 0.9, 0.98 and 0.98, respectively.

Conclusion

The novel VR platform is highly accurate and reliable in determining both acetabular cup and femoral stem component orientations in simulated THR models. This adaptable and cost-effective digital tracking platform may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery.

Radiologic restoration inaccuracy increases postoperative dislocation in primary total hip arthroplasty: a retrospective study with propensity score matching

BACKGROUND

Dislocation is a complicated process and associated with multivariate etiology and risk factors. The purpose of this study was to verify if radiologic restoration inaccuracy increases postoperative dislocation in primary total hip arthroplasty (THA) individually or synergistically.

METHODS

From 2017 to 2020, we identified 76 (1.9%) patients who suffered postoperative dislocations from 3926 THAs in our institution. After excluded patients with previously proven patient-related and implant-related risk factors, the remaining patients were used to match a 1:1 control patients who were without dislocation. The cup position (inclination and anteversion angles), hip offset (HO), leg length discrepancy (LLD), and abductor lever arm (ALA) were analyzed by univariate analyses and multivariate logistic regressions.

RESULTS

Measurements on radiographs showed excellent interobserver agreement (intraclass correlation coefficient (ICC) 0.922-0.952) and intraobserver agreements (ICC 0.933-0.967). HO restoration inaccuracy (without ± 5 mm) was associated with higher dislocation risk (OR 4.241 95% CI 1.440-12.492, P = 0.009). The restoration inaccuracy of the cup position, LLD, or ALA could not increase the dislocation risk individually. When combining the radiologic restoration inaccuracy factors, the HO + LLD restoration inaccuracy and HO + ALA restoration inaccuracy increased the odds of postoperative dislocation (OR 12.056, 95% CI 1.409-103.127, P = 0.023; OR 4.770, 95% CI 1.336-17.028, P = 0.016, respectively). Combining the four risk factors of cup safe zone, HO, LLD, and ALA, patients with 3 or 4 radiologic restoration inaccuracy factors showed a higher risk of dislocation (OR 13.500, 95% CI 1.340-135.983, P = 0.027).

CONCLUSION

Hip offset (HO) restoration inaccuracy increased the risk of dislocation following primary THA. Multivariate radiologic restoration accuracy is critical for the prevention of dislocation and needs to be valued by surgeons.

Elucidation of target implant orientations with the safety range of hip rotation with adduction or abduction during squatting: Simulation based on in vivo replaced hip kinematics

Objectives: The study aimed to elucidate target cup orientation and stem anteversions to avoid impingement between the liner and stem neck even at hip rotation with adduction during the deeply flexed posture.

Methods: A computer simulation analysis was performed on 32 total hip arthroplasty patients applying patient-specific orientation of the components and in vivo hip kinematics obtained from three-dimensional analysis of the squatting motion. The anterior/posterior liner-to-neck distance and impingement were evaluated based on a virtual change in internal/external rotation (0°–60°) and adduction/abduction (0°–20°) at actual maximum flexion/extension during squatting. Cutoff values of cup orientations, stem anteversion, and combined anteversion to avoid liner-to-neck impingements were determined.

Results: The anterior liner-to-neck distance decreased as internal rotation or adduction increased, and the posterior liner-to-neck distance decreased as external rotation or adduction increased. Negative correlations were found between anterior/posterior liner-to-neck distances at maximum flexion/extension and internal/external rotation. Anterior/posterior liner-to-neck impingements were observed in 6/18 hips (18/56%) at 45° internal/external rotation with 20° adduction. The range of target cup anteversion, stem anteversion, and combined anteversion to avoid both anterior and posterior liner-to-neck impingements during squatting were 15°–18°, 19°–34°, and 41°–56°, respectively.

Conclusion: Simulated hip rotations caused prosthetic impingement during squatting. Surgeons could gain valuable insights into target cup orientations and stem anteversion based on postoperative simulations during the deeply flexed posture.