Preoperative templating is a valuable and widely accepted tool in the planning of total hip arthroplasty (THA), assisting surgeons in determining the appropriate size, alignment, and positioning of prosthetic components1. Traditionally, templating was performed using acetate overlays placed on printed radiographs; however, with advances in imaging technology, digital templating has become increasingly prevalent2. Accurate templating has been shown to optimise biomechanical parameters such as leg length discrepancy (LLD), femoral offset, centre of rotation, and component alignment, thereby improving implant stability, reducing operative time, and minimising wear secondary to malposition. Improved biomechanics are expected to translate into better functional outcomes and enhanced longevity of the prosthesis.3 Previous studies have demonstrated good intra- and inter-observer reliability for templating of uncemented acetabular and femoral components, although accuracy is comparatively lower for predicting femoral neck length. Total hip arthroplasty remains the definitive surgical treatment for end-stage osteoarthritis of the hip, with additional indications including femoral neck fractures, avascular necrosis of the femoral head, hip dysplasia, and inflammatory arthritis4,5. Since its introduction in the 1960s, THA has consistently demonstrated excellent long-term outcomes, leading it to be described as the “operation of the century.” Despite its success, post-operative leg length discrepancy remains a well-recognised complication, with reported incidence ranging from 1% to 27%, and is a major contributor to patient dissatisfaction and medicolegal claims. Limb lengthening is generally more poorly tolerated than shortening, with discrepancies ranging from 3 mm to 70 mm reported in the literature.6 While minor discrepancies (<5 mm) are often asymptomatic and moderate discrepancies (5–10 mm) are usually manageable, severe discrepancies (>10 mm) can result in significant pain, gait disturbance, and functional impairment. Another early post-operative complication of concern is hip dislocation, highlighting the intra-operative challenge of restoring limb length without compromising joint stability. This balance is achieved through accurate restoration of the hip centre of rotation and femoral offset, both of which are essential for optimal abductor muscle function and normal gait mechanics. Digital templating software allows precise calculation of radiographic magnification and enables accurate measurement of leg length using reliable pelvic and femoral landmarks, while also assisting in determining the appropriate level of femoral neck osteotomy7,8. Although digital templating is recommended by professional orthopaedic bodies and has demonstrated high accuracy, its availability may be limited in resource-constrained settings.9 Therefore, this study aims to evaluate the role of templating—particularly digital versus conventional methods—in restoring limb length discrepancy and femoral offset in patients undergoing THA, while also exploring simpler, cost-effective alternatives for implant size prediction in resource-limited environments10-12. AIM To determine the relation between Templated implant size & Chosen implant size in Total Hip Arthroplasty Patients in view of Limb Length Discrepancy.

The study was conducted in the Department of Orthopedics, Dr. S. N. Medical College, Jodhpur, as a retrospective observational study over a one-year period from February 2023 to February 2024. A consecutive sampling technique was employed to include all eligible patients who underwent total hip arthroplasty during the study period. A total of 33 patients were initially enrolled, all of whom had documented details of the chosen implant. However, complete and adequate true-size radiographs required for accurate templating were available for 30 patients, while 3 patients were excluded due to incomplete or unavailable radiographic data. Consequently, templating data from 30 patients were analysed. Eligibility criteria included patients aged 18 to 80 years of either gender who underwent unilateral total hip arthroplasty for primary osteoarthritis of the hip, unilateral avascular necrosis of the femoral head, unilateral fracture neck of femur, or acute unilateral hip trauma, with diagnosis confirmed on anteroposterior radiographs of bilateral hips with pelvis. Patients were excluded if they had old fractures involving both hip joints, bilateral osteoarthritis of the hip, revision hip arthroplasty, systemic disorders leading to secondary hip osteoarthritis, or acute trauma resulting in bilateral hip fractures. This selection ensured a homogeneous study population suitable for evaluating the role of templating in unilateral total hip arthroplasty outcomes.

Table 01: Demographics and Clinical Features Variable Mean SD Age (Mean±SD) 45.80±16.48 16.48 Total of 30 patients were enrolled in the study with the mean age of 45.80±16.48. Table 2:Effected side Side Right 15 50% Left 15 50% The condition affects the right and left sides equally, with 15 participants (50%) for each side. Table 3: Duration of hospital stay Mean SD Longevity of Hospital Stay (Days) 5.57 1.22 The mean hospital stay duration is 5.57±1.22 days. Table 4: Acetabular cup size Acetubular Cup Size Mean SD Templated 51.87 2.56 Chosen 51.60 2.54 Femoral Stem Size Templated 4.00 1.68 Chosen 4.03 1.81 The mean acetabular cup size is 51.87±2.56 for templated and 51.60±2.54 for chosen sizes. The femoral stem size is 4.00±1.68 for templated and 4.03±1.81 for chosen sizes. Table 5: Complications Complications Number Percentage Hip swelling 1 3.3% Infection 1 3.3% Pain 1 3.3% Swelling 1 3.3% Complications are minimal, with hip swelling, infection, pain, and swelling each occurring in 1 participant (3.3%). Table 6: Interpretation of Prediction Accuracy and Correlation Accurate +/- 1 size difference +/-2 size difference PCC Femur stem size 11 (36.6%) 24 (80%) 29 (96.6%) 0.998 Acetabular cup size 7 (23.3%) 19 (63.3%) 25 (83.3%) 0.990 For the femur stem size predictions, 11 out of 30 cases (36.6%) were accurately templated, while 24 out of 30 cases (80%) were within a +/- 1 size difference, and 29 out of 30 cases (96.6%) were within a +/- 2 size difference. Similarly, for the acetabular cup size predictions, 7 out of 30 cases (23.3%) were accurately templated, 19 out of 30 cases (63.3%) were within a +/- 1 size difference, and 25 out of 30 cases (83.3%) were within a +/- 2 size difference. Table 7: Limb length discrepancy Variable > - 10mm -10 mm >/= -5mm 10mm Number of patients 2 5 3 9 6 3 2 The distribution of limb length discrepancies indicates that the majority of patients (9 out of 30) achieved equal limb lengths, suggesting effective surgical outcomes for limb length correction. The data also shows that smaller discrepancies (within +/- 5 mm) were more common compared to larger discrepancies (greater than +/- 10 mm), highlighting the precision and accuracy of the surgical procedures. Table 8: Femur Stem Size and Acetabular Cup Size Differences Variable -4 -3 -2 -1 Equal 1 2 3 4 Femur stem size 0 0 2 5 11 8 3 1 0 Acetabular cup size 1 1 2 5 7 7 4 1 2 The data shows that the majority of patients achieved either equal sizes or a small size difference of +/- 1, demonstrating effective templating techniques for both femur stem size and acetabular cup size. Table 9: Comparison of Variables Based on Side Operated Variable Side Operated p-value Right (%) Left (%) Age 47.27±17.84 44.33±15.48 0.634 Oxford Score 15 Days 23.0±3.22 22.20±1.37 0.385 1 Month 20.93±3.05 20.33±1.11 0.481 3 Month 18.0±3.58 16.0±2.13 0.074 6 Month 14.80±0.94 14.80±0.94 0.076 Templated Acetabular Cup Size 51.47±2.66 52.27±2.49 0.403 Templated Femoral Stem Size 3.53±1.8 4.47±1.45 0.131 Diagnosis AVN 10 (66.7) 11 (73.3) 0.060 NOF 0 (0) 3 (20) OA 4 (26.7) 0 (0) TB 0 (0) 1 (6.7) Tom Smith Arthritis 1 (6.7) 0 (0) The mean age for participants operated on the right side is 47.27±17.84 years, while for those operated on the left side, it is 44.33±15.48 years, with a p-value of 0.634, indicating no significant difference. The Oxford Hip Score at various time intervals post-intervention shows no significant differences between sides, with p-values of 0.385 at 15 days, 0.481 at 1 month, 0.074 at 3 months, and 0.076 at 6 months. Templated acetabular cup size has a mean of 51.47±2.66 for the right side and 52.27±2.49 for the left side, with a p-value of 0.403, indicating no significant difference. The templated femoral stem size has a mean of 3.53±1.8 for the right side and 4.47±1.45 for the left side, with a p-value of 0.131, also indicating no significant difference. The diagnosis distribution shows 10 cases (66.7%) of AVN Hip on the right side and 11 cases (73.3%) on the left side. There are no cases of NOF on the right side, but 3 cases (20%) on the left side. OA Hip has 4 cases (26.7%) on the right side and none on the left, with a p-value of 0.060, suggesting a borderline significant difference. TB Hip and Tom Smith Arthritis each have 1 case (6.7%) on the right side and none on the left side for Tom Smith Arthritis, and 1 case (6.7%) on the left side for TB Hip.

In this study we found an acceptable accuracy for templating the femoral stem, with 80%being within+/−1 size compared to the template. A PCC of 0.998 is interpreted as a high correlation. We found lower accuracy for templating the acetabular shell, with 63.3% within +/−1size, and a PCC of 0.990 a high correlation. All patients were scheduled for total hip arthroplasty using a specific company, uncemented acetabular shell and uncemented femoral stems with fixed neck component, so there is no need for separated neck length templating. An accuracy of up to 90–100% has been reported for both acetabular and femoral implants. But many studies concerning accuracy and precision in templating THA are not blinded, at least not expressively so. One might argue, that each surgeon templates according to how he/she operates, so that in a clinical setting the surgeon must perform his own templates. In contrast, when an evaluation of a method is performed, that a surgeon is biased by her templates, so a significant bias towards correlation exists There are no absolute criteria to evaluate this. But we did try to evaluate the biomechanical result of the operation by measuring leg length discrepancy, as leg length equalization usually is one of the most important goals of THA. We did not evaluate medial offset or anteversion and inclination of the acetabular shell. This could have further improved the biomechanical evaluation. However, due to stem design, offset and leg length is interdependent. Peroperatively, one must regularly prioritize one over the other, and leg length discrepancy is more often a patient complaint. Also, femoral neck version is a confounder that cannot be determined by templating on frontal x-rays. Conversely, the other components may not have been seated as deeply as planned. The main constraint on elongation during surgery is tissue tension, which is impossible to predict accurately while templating. Altogether, this strengthens the argument that per operative observations must override preoperative planning. Radiological leg length discrepancy is not equal to clinical leg length discrepancy. Transient functional leg length discrepancy may also occur. However, for the sake of evaluation of templating as a method, we focused on the more objective radiological measurements There is no consensus on what the threshold for clinically significant leg length inequality is.15 We found that 87% had leg length equality within +/−10 mm, which in usually regarded as clinically insignificant. There are a few limitations of our study. It was carried out in only one clinic, but it is unclear how a multicentre evaluation might enhance our findings. Also, as a tertiary referral centre, we may have seen more pronounced preoperative pathology than what is typical elsewhere, even in primary THA. Templating, as well as surgery, is more challenging in these situations. The number of observations is not very large, but our power analysis suggests that the number is sufficient to yield significant results. Also, our sample population had an adequate distribution of all values to make the analyses meaningful. There is no golden standard that we could compare our results with. But this is a general and main objection to preoperative templating of joint prostheses. We concede that radiographic interpretation relies on the clinician’s experience with reading hip radiographs. Main sources of errors when measuring radiographs are errors in locating corresponding landmarks, and errors in calibration on radiographs. However, previous findings suggest that above a certain threshold of experience, this is mainly a methodological problem, and is not likely to infer further bias to our results.

The acetabular component was templated accurately in 23.3%, while 63.3% was within +/− 1 component size difference, and 83.3% was within +/−2 size differences. The femoral stem was templated accurately in 36.6%, while 80% was within +/− 1 component size difference, and 96.6% was within +/−2 size differences.. 64% of patients experienced radiologic equalization within +/− 5mm, and 86.6% within 10mm. 15% had leg length discrepancy of more than 10mm postoperatively. There was no systematic tendency to overestimate or underestimate leg length peroperatively. Preoperative planning and templating play an important role in modern hip joint reconstruction and likely improve the probability of achieving a successful outcome in THA. Preoperative planning helps the surgeon decide the type, size and position of the femoral and acetabular components in addition to giving information on offset and leg length parameters that must be restored, while allowing this to be performed in an expeditious and accurate manner. As a final note, while preoperative radiographic templating gives the surgeon an operative road map to follow, final surgical decisions will be based on intraoperative factors that continue to rely on surgical experience. In conclusion, we find that the accuracy of templating in uncemented THA is acceptable for the femoral stem, but somewhat inferior for the acetabular shell. Templating is a useful tool in preoperative planning, but cannot be regarded as a blueprint for the operative choice.

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