Preoperative Templating Research Articles

Predicting range of movement after knee replacement: the importance of posterior condylar offset and tibial slope

We have attempted to quantify the influence of clinical, radiological and prosthetic design factors upon flexion following knee replacement. Our study examined the outcome following 101 knee replacements performed in two prospective randomized trials using similar cruciate retaining implants. Multivariate analyses, after adjusting for age, sex, diagnosis and the type of prosthesis revealed that the only significant correlates for range of movement at 12 months were the difference in posterior condylar offset ratio (p < 0.001), tibial slope (p < 0.001) and preoperative range of movement (p = 0.025). We found a moderate correlation between 12-month range of movement and posterior tibial slope (R = 0.58) and the difference of post femoral condylar offset (i.e, post-operative minus preoperative posterior condylar offset, R = 0.65). Posterior condylar offset had the greatest impact upon final range of movement highlighting this as an important consideration for the operating surgeon at pre-operative templating when choosing both the design and size of the femoral component.

Value of Preoperative Templating for Primary Total Knee Arthroplasty

The value of preoperative templating for primary total knee arthroplasty (TKA) has recently been questioned. In our clinical practice, preoperative templating is valuable for sizing components and achieving optimal coronal alignment. We preoperatively templated the size of femoral and tibial components, the distal femoral valgus cut, and the proximal tibial cut for 200 primary TKAs. Preoperative templating predicted the exact size of 165 (82.5%) femoral and 159 (79.5%) tibial components, with 194 (97%) femoral and 185 (92.5%) tibial components templated to within one size used. Postoperative tibiofemoral alignment was within +/- 3 degrees of the goal alignment in 189 (94.5%) knees. Postoperative femoral and tibial component coronal alignment was within +/- 3 degrees of the goal coronal alignment in 190 (95%) and 199 (99.5%) knees, respectively. The accuracy of component sizing in this study is greater than previously reported. The prevalence of alignment outliers in this study is less than previously reported for conventional techniques.

Cementless Total Hip Arthroplasty with Medial Wall Osteotomy for the Sequelae of Septic Arthritis of the Hip

BackgroundWe performed a retrospective study to evaluate the results of acetabular circumferential medial wall osteotomy, a procedure designed to provide secure fixation of a cementless hemispherical acetabular cup for the sequelae of septic arthritis of the hip.MethodsWe assessed 38 total hip arthroplasties (THAs) with circumferential acetabular medial wall osteotomies performed on patients with sequelae of septic arthritis of the hip between 1993 and 2000, who were followed up for ≥ 3 years. The average follow-up period was 8.3 years (range, 3 to 12 years). The indication for this technique was poor acetabular cup coverage of ≤ 70% on preoperative templating. In all cases, cementless hemispherical acetabular cups were fixed to the true acetabulum. Additional procedures included soft tissue release in 16 hips and femoral derotational and shortening osteotomies in 12 hips. We evaluated both clinical and radiological results.ResultsThe Harris hip scores improved from 57 points preoperatively to 91 points postoperatively. Radiological analysis revealed no aseptic loosening or radiolucent lines around the acetabular cup. Stable bony fixation of the acetabular cup in the true acetabulum was seen in all cases. Acetabular osteolysis was demonstrated in 12 hips. Revision surgery was performed in 6 hips, but there were no complications related to acetabular circumferential medial wall osteotomy.ConclusionsCircumferential acetabular medial wall osteotomy can provide appropriate positioning and sufficient coverage of the acetabular cup and thus preserve the medial wall thickness in cementless THA without the need for additional bone grafting for the sequelae of septic arthritis of the hip.

Disc calibration for digital templating in hip replacement

Digital radiography is becoming widespread. Accurate pre-operative templating of digital images of the hip traditionally involves positioning a calibration object at its centre. This can be difficult and cause embarrassment. We have devised a method whereby a planar disc placed on the radiographic cassette accounts for the expected magnification. Initial examination of 50 pelvic CT scans showed a mean hip centre distance of 117 mm (79 to 142) above the gluteal skin. Further calculations predicted that a disc of 37.17 mm diameter, placed on the cassette, would appear identical to a 30 mm sphere placed at the level of the centre of the hip as requested by our templating software. We assessed accuracy and reproducibility by 'reverse calibration' of 20 radiographs taken three months after hip replacement using simultaneous sphere and disc methods, and a further 20 with a precision disc of accurate size. Even when variations in patient size were ignored, the disc proved more accurate and reliable than the sphere. The technique is reliable, robust, cost effective and acceptable to patients and radiographers. It can easily be used in any radiography department after a few simple calculations and manufacture of appropriately-sized discs.

A New Digital Preoperative Planning Method for Total Hip Arthroplasties

Preoperative templating is an important part of a THA. The ability to accurately determine magnification of the hip on the radiograph and apply identical magnification to the radiograph and template will improve accuracy of preoperative templating of THA. We designed a templating method using a new way of determining the hip magnification with a linear relationship between magnification of the hip and the reference object on top of the pubis symphysis; the relationship was determined on 50 radiographs. We then compared our method with two other templating methods: an analog method assuming an average hip magnification of 15% and a digital method determining the hip magnification with a one-to-one relationship between the reference object and the hip. All methods were reproducible. Uniform undersizing occurred when templating with the digital method based on the one-to-one relationship; the analog method best predicted the implanted prosthesis size, closely followed by our new digital templating method; the new method will be particularly applicable for preoperative THA when analog methods are replaced by digital methods.

Digital pre-operative templating is more accurate in total hip replacement compared to analogue templating

We prospectively evaluated the accuracy of digital compared to analogue pre-operative templating in 50 consecutive primary hip replacements between April 2006 and June 2007. The senior author pre-operatively templated implant size using TraumaCad (Orthocrat Limited, Israel). Thirty-one Exeter primary hip and 19 hybrid hip replacements were performed. Hips were templated using radiographs calibrated against a spherical metal ball. For each hip, an AP pelvis view was used. Acetabular implants used were either Trident PSL or Exeter contemporary cup (Stryker). Femoral stem was Exeter (Stryker). Predicted implant sizes were documented. Post-operatively, the predicted implant size was compared to the implanted components. All post-operative films showed good fit of components and there were no intraoperative or post-operative fractures. The intra-rater reliability (ICC) of analogue templating was 0.96 and digital templating was 0.90. Accurate templating score for acetabular cup was 46% (digital) 43% (analogue), femoral offset was 80% (digital) 70% (analogue), femoral stem was 76% (digital) 60% (analogue). The differences between templating and actual implant sizes were plotted in Bland–Altman plot. Digital templating produced narrower confidence interval compared to analogue templating. Digital templating proved to be statistically, significantly more accurate compared to analogue templating for acetabluar cup and femoral stem. Our data indicate that digital templating is more reliable in predicting actual implant sizes for total hip arthroplasty when performed by the operating surgeon.

Less Invasive TKA

Femoral intramedullary canal referencing is used by most knee arthroplasty systems. Fat embolism, activation of coagulation, and bleeding may occur from the reamed canal. The purpose of our study was to evaluate a new extramedullary device that relies on templated data. We randomized 100 consecutive patients undergoing primary total knee arthroplasty through a limited parapatellar approach to use of either standard intramedullary femoral instruments (IM group) or a new extramedullary device (EM group). The extramedullary instrument was calibrated using templated data obtained from a preoperative full-limb weightbearing anteroposterior view of the knee. In both groups, an intraoperative double check was performed using an extramedullary rod referring to the anterosuperior iliac spine. Femoral component coronal alignment was within 0 degrees +/- 2 degrees of the mechanical axis in 84% of the IM group and 86% of the EM group. Sagittal alignment of the femoral component was 0 degrees +/- 2 degrees in 78% of the IM group and 90% of the EM group. We observed no difference in the average operative time between the two groups. The two groups showed similar postoperative blood loss. Extramedullary reference with careful preoperative templating can be safely used during TKA. Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Determination of femoral component size in unicompartmental knee replacement

It is difficult to determine the ideal size of femoral component when a unicompartmental knee replacement (UKR) is implanted with a minimally invasive approach. The aim of the study was to identify the best method of determining femoral component size pre-operatively. This was done by assessing the accuracy with which it could be predicted by pre-operative templating, patient height, gender and tibial component size. One hundred patients who had had Oxford UKR were studied. Pre-operative radiographs were templated and patient height, gender and implanted tibial component size were recorded. From a review of post-operative radiographs and the known size of component used the ideal size of component that should have been used was established. By relating patient height, gender and tibial component size to the ideal femoral component size the range of these various parameters that best predicted each component size was identified. The reliability of these predictions was assessed assuming that a component one size off ideal was acceptable and two sizes off was unacceptable. Templating was correct in 67% of cases, acceptable in 33% and was never unacceptable. Height alone was correct in 56%, acceptable in 38% and unacceptable in 6%. Height based on gender was correct in 75%, acceptable in 25% and was never unacceptable. Tibial size was correct in 56%, acceptable in 41% and unacceptable in 3%. We conclude that both templating and height based on gender are reliable methods of assessing femoral component size. However because errors can occur surgeons are advised to use both.

Computer assisted orthopedic surgery; its influence on prosthesis size in total knee replacement

Improvement of alignment and position of the components in TKAs using Computer Assisted Orthopaedic Surgery (CAOS) has been described. However, much less is known about the accuracy of CAOS in determining the size of the components. The purpose of this study was to evaluate the size of the femoral and tibial component using the CAOS system from Brainlab. The component sizes were compared to pre-operative templating and post-operative scoring the adequateness of size. Forty TKAs (NexGen) were evaluated: 20 using CAOS and 20 conventional. Statistical analysis of the templated and implanted size indicated a fair agreement for the femur (kappa 0.38) and the tibia (kappa 0.35). In the CAOS group significantly more oversizing occurred for the femoral component ( p = 0.020). No significant difference was found for the tibial component. We conclude there is a risk of oversizing the femoral component of the NexGen system when using CAOS.

Comparison of digital and plain radiography preoperative templating in total knee arthroplasty

We present the results of prospective evaluation of digital compared to plain radiographic pre-operative templating for primary total knee replacement. All consecutive patients undergoing primary knee replacement under the senior author (AS) were eligible. Patients with previous knee replacement or without calibrated digital or plain radiographs were excluded. Plain radiographs were templated against acetate templates supplied by the manufacturer. Digital images were templated with the help of commercial software TraumaCad. A 25mm spherical metal ball placed nearest to the affected knee joint acted as calibration object. AS performed all the templating. The ICC value for intra-rater reliability was 0.846 for tibial templating and 0.840 for femoral templating. PFC sigma cruciate substituting components were implanted in all patients. 28 consecutive patients between April 2006 and June 2007 were included. Accurate digital templating score was 80% for tibial implant and 40% for femur. Accuracy of analog templating was 55% for tibial implant and 50% for femur. There was no mismatch of over one size. The differences between templated and implanted sizes were plotted against their mean in Bland-Altman plot. The 95% confidence interval of the differences between digital and actual sizes were: 0.78 to − 0.75 sizes for tibial implant and 1.15 to −0.93 sizes for femoral implant. The 95% confidence interval of the differences between plain and actual sizes were: 0.38 to −0.99 size for tibial implant and 0.93 to −1.32 size for femoral implant. The two tailed P value for difference between digital and analog templating from a Wilcoxon matched pair signed rank test was 0.021 for tibia and 0.006 for femur. We found preoperative templating by the operating surgeon reliable and accurate but digital templating did not offer any additional advantage.

Optimizing glenoid component position using three-dimensional computed tomography reconstruction

Glenoid implant design and alignment are critical to the success of shoulder arthroplasty. Computer-aided design models of 3 glenoid implant designs (keel, standard pegs, and modified pegs) were virtually implanted into 3-dimensional computed tomography-reconstructed models of 40 normal scapulae. The incidence of perforation on 3-dimensional computed tomography preoperative templating varied from 8% to 18% for the 3 models. Malalignment of the implants in retroversion was better tolerated than anteversion and varied with implant design. Tolerance for medialization of the implant to correct for glenoid wear was limited (range, 0 degrees-18 degrees ) and varied with implant design. The modified peg design had the lowest incidence of perforation, the greatest tolerance for malalignment, and the ability to correct for glenoid wear effects. These results emphasize the need for accurate preoperative templating and for developing alignment guides or surgical navigation tools for shoulder arthroplasty and may be used to improve implant fixation designs.

The Accuracy of Preoperative Templating in Cementless Total Hip Arthroplasty

We evaluated the accuracy and clinical usefulness of preoperative templating in 109 cementless total hip arthroplasties. The size of the prosthesis was exactly predicted in 46 (42.2%) acetabular and 75 (68.8%) femoral components. The accuracy increased to greater than 90% if the prosthesis size was within 1 or 2 sizes (above or below) for femoral component and acetabular components, respectively. Having a contralateral total hip arthroplasty as a guide for preoperative templating was associated with greater accuracy in predicting the femoral component size only. Eighty-eight percent of the acetabular components were oriented inside the presumed safe range for inclination; 42% of the acetabular components were in the presumed safe range of anteversion. The mean postoperative leg length discrepancy was 0.9 ± 6.8 mm; 93.5% had a discrepancy within 10 mm.

Quantitative Anatomy of Subaxial Cervical Lateral Mass

Determination of lateral mass screw lengths with Roy-Camille and Magerl techniques of screw insertion using computerized tomography in 98 young, asymptomatic North American volunteers. To provide reliable and normative data on safe screw lengths using the Roy-Camille and Magerl techniques of lateral mass fixation in the subaxial cervical spine. Lateral mass screw lengths have been studied in the past using differing subject and measurement characteristics and small sample sizes. Results demonstrated considerable variation in screw length and influencing factors. Inappropriate screw lengths can result in neurovascular injury during screw insertion, facet joint damage, or inadequate fixation. Bicortical screw lengths were bilaterally measured at each spinal level from C3-C7 in 98 young volunteers using computed tomography reconstructions through the lateral masses obtained in the plane of the screw in Roy-Camille and Magerl techniques. With both techniques, trajectories were longest at C4-C6, shorter at C3, and shortest at C7. Screw lengths were greater in males when compared with females at all levels. Average Magerl screw lengths were approximately 2.6 mm longer at C3-C6 levels, and approximately 1.3 mm longer at the C7 level when compared with Roy-Camille technique. There was minimal correlation between screw lengths and anthropometric measurements including stature, body weight, and neck length. Significant variations exist at each subaxial level with either technique. We recommend the surgeon determine screw lengths for fixation at each level using preoperative sagittal oblique computed tomography scans, which provide the most accurate technique of preoperative templating for screw length.

Application of computer-aided design in preoperative planning in total hip replacement

To investigate the advantages of using the preoperative computer-aided design system (CAD) in total hip replacement (THR). From March 2002 to September 2005, 182 patients who underwent primary THR were screened and divided into 2 groups randomly. CAD and traditional preoperative templating were used in preoperative planning respectively. In group using CAD, the migration of the center of acetabulum was smaller, and the discrepancy of the limb length and the abductor force lever arm were fewer. All the differences above were significantly different. CAD helps remove much of the guesswork during surgery, and the implant can be more precise fitting to the patient. And equal limb lengths and balanced abductor force can be restored more accurately.

A Comparison of Acetate and Digital Templating for Total Knee Arthroplasty

Accurate preoperative templating can facilitate precise, efficient, and reproducible total knee arthroplasty. We determined whether acetate templating accurately predicted knee implants used and compared the accuracy of digital templating. Preoperative planning was performed on 50 consecutive preoperative radiographs during 2005. After digital images were obtained, appropriately magnified analog films were printed. Four arthroplasty surgeons and one resident performed acetate templating and one arthroplasty surgeon trained in the technique performed digital templating. Acetate and digital templating accurately predicted the size of the implanted component to within one size, 91% versus 93%, respectively. The digital technique was more accurate than acetate for tibial component size. Acetate and digital templating did not differ in predicting femoral component size. Our data suggest digital templating is at least as accurate as traditional acetate templating for predicting knee implant sizing. Level II, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Effect of Anesthesia Type on Limb Length Discrepancy After Total Hip Arthroplasty

A retrospective study of 132 patients (63 spinal anesthesia and 69 general anesthesia) undergoing total hip arthroplasty was performed by 4 fellowship-trained adult reconstructive surgeons to determine the influence of anesthesia type on postoperative limb length and medial offset. Limb length discrepancy occurred in 87.0% of patients who received regional anesthesia as opposed to 47.6% patients who had general anesthesia ( P < .001). Differences in postoperative medial offset measurements between the 2 groups were not statistically significant. It was concluded that surgeons operating on patients who receive regional anesthesia should supplement intraoperative tests for assessing hip stability with meticulous preoperative templating to avoid overlengthening the operative limb.

Relationship Between Femoral Head Size and Distance to Lesser Trochanter

Hemiarthroplasty of the hip is a common treatment for displaced fractures of the femoral neck. However, accurate restoration of leg length may be difficult to achieve because intraoperative measurements of leg length and preoperative templating are limited by the fracture. Our primary question was whether femoral head diameter can be used to predict femoral head height. We analyzed 34 cadaveric femora to determine diameter of the femoral head, distance from the lesser trochanteric sulcus to the external center of the femoral head (head height), lateral distance from the proximal tip of the greater trochanter to the center of the femoral head (offset), and the femoral neck/shaft angle. The femoral head diameter had a linear correlation with head height expressed by the following equation: head height = 1.035 x femoral head diameter. Our results indicate the diameter of the femoral head is similar in size to the distance from the top of the lesser trochanter to the center of the femoral head in an average population of cadavers. This may be a helpful clinical measurement to assess leg length during surgical treatment of hip fractures.

Accuracy of Femoral Templating in Reproducing Anatomical Femoral Offset in Total Hip Replacement

Restoration of hip biomechanics is a crucial component of successful total hip replacement. Preoperative templating is recommended to ensure that the size and orientation of implants is optimised. We studied how closely natural femoral offset could be reproduced using the manufacturers' templates for 10 femoral stems in common use in the UK. A series of 23 consecutive preoperative radiographs from patients who had undergone unilateral total hip replacement for unilateral osteoarthritis of the hip was employed. The change in offset between the templated position of the best-fitting template and the anatomical centre of the hip was measured. The templates were then ranked according to their ability to reproduce the normal anatomical offset. The most accurate was the CPS-Plus (Root Mean Square Error 2.0 mm) followed in rank order by: C stem (2.16), CPT (2.40), Exeter (3.23), Stanmore (3.28), Charnley (3.65), Corail (3.72), ABG II (4.30), Furlong HAC (5.08) and Furlong modular (7.14). A similar pattern of results was achieved when the standard error of variability of offset was analysed. We observed a wide variation in the ability of the femoral prosthesis templates to reproduce normal femoral offset. This variation was independent of the seniority of the observer. The templates of modern polished tapered stems with high modularity were best able to reproduce femoral offset. The current move towards digitisation of X-rays may offer manufacturers an opportunity to improve template designs in certain instances, and to develop appropriate computer software.

Preoperative templating of femoral components on plain X-rays

Preoperative femoral templating for total hip arthroplasty (THA) has been performed by antero-posterior radiographs of both hips which should be taken with the femur rotated internally to reduce the effect of femoral anteversion. However, there is no criterion to evaluate the optimal rotated radiograph. Here, we quantitatively investigated 50 femora whether the thickness of the lesser trochanter (TLT) was useful when evaluating the femoral rotation, and assessed the effect of prosthetic templating on the inappropriate rotated radiographs. We assessed 50 femora of 46 consecutive osteoarthritic patients using "synthetic X-ray" based on computer tomography (CT) images, which can be displayed as virtual plain radiographs with any magnification and any projected direction such as plain radiographs. We made four femoral radiograph groups of different rotation prepared (neutral, 15 degrees, 30 degrees, and 45 degrees external rotation), and measured the TLT. We also templated femoral stem on the different rotated synthetic X-ray of each patient, and investigated the effect of inappropriate rotated radiograph by the measurement of the position and the size of the stem. Seventy-four percent of the neutral rotational group had less than 5 mm of the TLT. While 30 degrees and 45 degrees external rotation group had few cases with less than 5 mm of the TLT. Compared to the neutral group, smaller stem size was selected in more than 80% cases of 30 degrees and 45 degrees external rotational group, and the stem position in these two groups was more than 5 mm proximally. We suggest that when templating femoral stem, this criterion "the TLT is less than 5 mm" reduces some risks by inappropriate rotated radiograph.

Cement Restrictor Function Below the Femoral Isthmus

Cement restrictors rely on achieving an interference fit with the wall of the medullary canal. Depending on the design of the cement restrictor, the intramedullary fit may be compromised as the femur starts to widen distally. Three different designs of cement restrictor were identified; universal, press-fit, and expandable. We determined which design of cement restrictor could resist the greatest pressures in a closed column of cement. Additionally, we recorded leakage of cement past the restrictor. We reamed synthetic femora to recreate the normal distal flare of the femur below the femoral isthmus. After inserting the cement restrictor, low-viscosity cement was gradually pressurized using an electronically controlled pneumatic ram. We then simultaneously recorded cement pressure above the cement restrictor and displacement of the cement restrictor. There was variation in the performance of the cement restrictors. The expandable cement restrictors resisted the greatest pressures. The resorbable expandable (REX Cement Stop) and press-fit cement restrictors reliably prevented cement leakage. The press-fit and universal restrictors failed at low pressures when deployed below the isthmus. The choice of cement restrictor may need to be modified if preoperative templating indicates the restrictor will sit below the femoral isthmus.