Identifying the center of the femoral head using ultrasonography to assess the higher accuracy of femoral extramedullary guides in TKA

Computer-aided robotics for applications in fracture reduction surgery: Advances, challenges, and opportunities

The advancement of information technology and AI has boosted global economic and social development. Robot systems (RS) and computer-aided technology (CAT) are used in various domains, including social production and human existence. Traditional fracture reduction surgery relies on the expertise and surgical skills of surgeons to realign fractures in patients. Researchers have developed robotic and assisted systems to automate fracture reduction surgery in recent decades. Computer-aided fracture reduction robot system (CARS) is used to replace the manual reduction performed by conventional physicians. A partial CARS has been used successfully in clinical fracture reduction surgery. This study provides an overview of CARS. First, the RS and CAT used in fracture reduction surgery are overviewed. Furthermore, a comprehensive analysis of CARS is presented, encompassing their design, experimental validation, and clinical applications, while highlighting recent advancements and potential future directions in this domain. The suggested CARS for fracture reduction are compared in different ways. The learning curve and technical ethics of CARS are summarized. The paper addresses unresolved research gaps and technical challenges, providing recommendations to guide future study.

TKA with retained hardware guided by intraoperative ultrasonography - a case report

Background

When a conservative management of gonarthrosis yields unsatisfactory results, a total knee arthroplasty (TKA) is recommended as an alternative approach. The implant survival is crucial for the long-term success of the procedure. However, in case of patients with retained hardware after past orthopedic procedures, providing correct alignment of the implant, which contributes to its longevity, is especially challenging. Here we present the use of an intra-operative ultrasonography for implant positioning in a 83-year-old male, undergoing TKA, without hardware removal, which was contraindicated due to his advanced age and comorbidities. Other imaging modalities taken into consideration are also described.

Case presentation

The right knee joint was approached with anterior incision. A femoral guide was introduced extramedullary. Ultrasonography was used to pinpoint the center of the femur’s head. Tibial’s guide was introduced intramedullary followed by a standard cut of the proximal part. Cemented ZIMMER NEXGEN prosthesis was used. Layered closure was applied. The placement of implant in neutral axis was confirmed on radiographs.

Conclusions

Our case demonstrates that ultrasonography might be helpful during TKA-procedure for implant positioning. However, more studies are needed to evaluate accuracy and application of ultrasound in the intraoperative settings.

The position of the centre of the femoral head relative to the midline of the pelvis: a consistent landmark in total knee replacement surgery

BACKGROUND

Femoro-tibial malalignment in excess of 3° is a recognised contributor of early mechanical failure in total knee replacement (TKR). Knowledge of the location of the centre of the femoral head is a pre-requisite to identification of the mechanical axis of the femur and can facilitate optimal component orientation. We investigated variation in the location of the centre of the femoral head relative to the midline of the pelvis.

METHODS

We analysed the pelvic radiographs of 150 patients with unilateral total hip replacements. The perpendicular distance from the centre of the femoral head of the non-operated hip to the centre of pubic symphysis was measured.

RESULTS

The mean distance from the centre of the femoral head to the pubic symphysis was 89.2mm (standard deviation, 5.7 mm). Patient height strongly correlated with this distance (r=0.53, p<0.01), as did the diameter of the femoral head (r=0.59, p<0.01). The latter was significantly larger in men than in women (50.9 mm vs. 44.5mm, p<0.01).

CONCLUSION

The results demonstrate that the position of the centre of the femoral head has very little variability, irrespective of patient age or body-mass index. If the gender-specific mean femoral head to midline distance is used to estimate the location of the femoral head centre, a line from this point to the centre of the femoral condyles will deviate from the true mechanical axis by no more than 1.5°, in 98% of cases.

Intraoperative assessment of resected condyle thickness in total knee arthroplasty

PURPOSE

The purpose of this study was to assess the use of resected condyle thickness measurement, obtained with caliper, when verifying the accuracy of distal femoral bone resection in total knee arthroplasty.

METHODS

Fifty-two total knee arthroplasties were performed to treat osteoarthritis with varus knee. The difference of caliper-measured thickness of resected medial and lateral femoral condyles after removal of cartilage from the lateral condyle was compared with radiographically measured values. The preoperative planned valgus cut angles and the postoperative femoral component valgus angles were compared.

RESULTS

The difference of radiograph-measured thickness averaged 2.4 ± 2.2 mm and the difference of caliper-measured thickness averaged 2.0 ± 2.1 mm (r = 0.735, P < 0.001). The postoperative femoral component valgus angle averaged 4.8° ± 1.6° (range, 2.0°-7.6°). The difference between the valgus cut angle and femoral component valgus angle averaged -0.3° ± 1.5°.

CONCLUSIONS

The confirmation of correspondence between the caliper-measured and radiographically measured thickness of resected condyles could verify the accuracy of distal femoral bone resection in total knee arthroplasty.

LEVEL OF EVIDENCE

III.

How precise is the identification of the center of the femoral head during total knee arthroplasty?

BACKGROUND AND PURPOSE

Identification of the center of the femoral head in the coronal plane is essential during total knee arthroplasty. We evaluated a new method for localization of the center of the hip, thereby detecting the neutral mechanical axis using inter-femoral head center distances (X) measured from a radiograph. Our proposed method was compared with 3 commonly used methods using landmarks that are estimated to be 2 finger-breaths medial to the anterosuperior iliac spine (method A), 2.5 cm perpendicular to the mid-inguinal point (method I), and 1.5 cm lateral to the femoral artery (method F).

METHODS

114 patients undergoing total knee arthroplasty were prospectively enrolled in the study. Four landmarks were marked and conventional anterior-posterior pelvic radiographs were taken. On the radiograph, the distance between the estimated FHC and the neutral mechanical axis was measured.

RESULTS

The median value (mm) of the measured distance was 9 in A, 7 in I, 8.5 in F, and 5 in X. When an error of more than 3° from neutral alignment was defined as an outlier, 15% of measurements in A, 6% of measurements in I, 14% in F, and 2% in X would fall in the outlier zone.

INTERPRETATION

The method detecting the neutral mechanical axis using inter-femoral head center distances (X) showed the least variability and the lowest percentage of outliers.

The analysis of risk factors in no thumb test in total knee arthroplasty

Background

We would like to analyze the risk factors of no thumb test among knee alignment tests during total knee arthroplasty surgery.

Methods

The 156 cases of total knee arthroplasty by an operator from October 2009 to April 2010 were analyzed according to preoperative indicators including body weight, height, degree of varus deformity, and patella subluxation and surgical indicators such as pre-osteotomy patella thickness, degree of patella degeneration, no thumb test which was evaluated after medial prepatella incision and before bone resection (1st test), no thumb test which was evaluated with corrective valgus stress (2nd test, J test), and the kind of prosthesis. We comparatively analyzed indicators affecting no thumb test (3rd test).

Results

There was no relation between age, sex, and body weight and no thumb test (3rd test). Patellar sulcus angle (p = 0.795), patellar congruence angle (p = 0.276) and preoperative mechanical axis showed no relationship. The 1st no thumb test (p = 0.007) and 2nd test (p = 0.002) showed significant relation with the 3rd no thumb test. Among surgical indicators, pre-osteotomy patella thickness (p = 0.275) and degeneration of patella (p = 0.320) were not relevant but post-osteotomy patellar thickness (p = 0.002) was relevant to no thumb test (3rd test). According to prosthesis, there was no significance with Nexgen (p = 0.575). However, there was significant correlation between Scorpio (p = 0.011), Vanguard (p = 0.049) and no thumb test (3rd test). Especially, Scorpio had a tendency to dislocate the patella, but Vanguard to stabilize the patella.

Conclusions

No thumb test (3rd test) is correlated positively with 1st test, 2nd test, and post-osteotomy patella thickness. Therefore, the more patella osteotomy and the prosthesis with high affinity to patellofemoral alignment would be required for correct patella alignment.

Variability in the range of inter-anterior superior iliac spine distance and its correlation with femoral head centre. A prospective computed tomography study of 200 adults

PURPOSE

The anterior superior iliac spine (ASIS) is commonly used to estimate the centre of the femoral head and assess limb alignment during surgical procedures. This study aimed to determine the range of inter-anterior superior iliac spine distances (IADs) and inter-femoral head centre distances (IFDs) among individuals and ascertain whether there is correlation between the IFD and the IAD. We also sought to determine whether gender, height and body mass index (BMI) had any influence on IAD and IFD.

MATERIALS AND METHODS

We prospectively measured IAD and IFD in 200 adults, using transverse computed tomography (CT) scans done for medical causes. We also calculated the distance between the pelvic midline and the centre of the femoral head (XY distance) from the measured IFD. The influence of gender, height and body-mass index on IAD and IFD, and the correlation of IAD with IFD, were also studied.

RESULTS

The overall mean IAD, IFD and XY distances were 22.7+/-1.6 cm, 16.0+/-0.8 cm and 8.0+/-0.4 cm, respectively. There was wide variation within the IAD range with 50% (100/200) of the subjects having their IAD within +/-10 mm of the mean compared to 75.5% (151/200) of the subjects with IFD within +/-10 mm of the mean. The probability that the mean XY distance would fall within 10 mm of the true femoral head centre in all subjects was 100%. The gender difference in IAD and IFD was statistically significant (P=0.03 and P<0.001, respectively), height and BMI had no influence, and the correlation of IAD with IFD was weak (0.35).

CONCLUSION

Although the range of IADs showed wide variation among subjects, this study clearly demonstrated the narrow range of the XY distance and IFD in the study population and provides a useful and accurate basis for a new method to determine the femoral head centre clinically and intraoperatively.

Placement of a palpable marker adjacent to the mid-inguinal point: assessment of a clinical method for detecting the femoral head centre during knee arthroplasty

Localization of the centre of the femoral head is vital when using extra-medullary femoral alignment systems in knee arthroplasty. This study investigated the accuracy of a palpable marker placed in the groin for detecting the centre of the femoral head. A table tennis ball, 38 mm in diameter, was taped 2.5 cm perpendicular to the mid-inguinal point in patients having a plain radiograph of the pelvis. The mean horizontal distance between the centre of the table tennis ball and a vertical line passing through the centre of the femoral head was 8.62 mm (range 0-28.6, SD 6.76). In 100% of cases the horizontal distance between the centre of the table tennis ball and a vertical line passing through the centre of the femoral head was less than one diameter of the table tennis ball. Using a theoretical mechanical axis model our clinical method would confer an error equal to or less than 2 degrees from the weight-bearing axis of the knee in up to 98% of cases. In conclusion, our results suggest that the clinical method reported here provides a simple and reliable way of localizing the centre of the femoral head in knee arthroplasty.

Computerized tomography scout view for determining distal femoral resection angle in intramedullary instrumentation of total knee arthroplasty

This study aims to investigate the results of distal femoral resection by determining the difference between mechanical and anatomical axes of femur using computerized tomography (CT) scout views in pre-operative planning of total knee arthroplasty. CT scout view of the lower extremities was taken before and after the operation in 16 patients undergoing total knee arthroplasty. Distal femoral resection was performed according to the previously determined ideal resection angle (IRA) using intramedullary instrumentation. At post-operative scanogram, femoral component deviation (FCD) was measured. The results were statistically analyzed. The average IRA was 6.95 (5-9) degrees. At post-operative measurements, the average FCD was 0.63 (0-3) degrees. CT scout films improve the accuracy in distal femoral resection and femoral component alignment.