Leg axis after computer-navigated total knee arthroplasty: a prospective randomized trial comparing computer-navigated and manual implantation

Sagittal component alignment is less reliable than coronal component alignment in a Chinese population undergoing navigated TKA

BACKGROUND

The purpose of our study was to determine whether postoperative sagittal component alignments of primary total knee arthroplasty (TKA) using the conventional and navigated technique differed significantly. Additionally, we determined whether the use of navigation systems resulted in hyperextension of the femoral components in Chinese patients.

METHODS

This retrospective study reviewed 36 consecutive patients (72 knees) who underwent simultaneous bilateral primary TKAs at our hospital from February 2011 to March 2012. One knee was replaced using a computer-assisted navigation system, and the contralateral knee was replaced with the conventional technique. The radiographic and clinical results of both groups were compared. The relationship between preoperative anatomic angles and component alignments in conventional TKA and navigated TKA was examined.

RESULTS

The radiographic results showed statistically significant differences only between the navigated and conventional groups for individual femoral coronal and sagittal component alignment. Femoral sagittal component alignment showed less deviation and tended to have hyperextension using the navigated technique (-0.35°) compared with the conventional technique (2.77°). There was no significant difference observed for the Knee Society Score (KSS) between the two groups at 2 years postoperatively.

CONCLUSIONS

The sagittal component alignment of primary TKA obtained using the conventional and navigated techniques differed significantly. Navigated TKAs resulted in a higher risk of hyperextension of the femoral components in Chinese patients.

Imageless computer navigation in total knee arthroplasty provides superior short term functional outcomes: a meta-analysis

Computer navigation in total knee arthroplasty (TKA) is intended to produce more reliable results, but its impact on functional outcomes has not been firmly demonstrated. Literature searches were performed for Level I randomized trials that compared TKA using imageless computer navigation to those performed with conventional instruments. Radiographic and functional outcomes were extracted and statistically analyzed. TKA performed with computer navigation was more likely to be within 3° of ideal mechanical alignment (87.1% vs. 73.7%, P < .01). Navigated TKAs had a higher increase in Knee Society Score at 3-month follow-up (68.5 vs. 58.1, P = .03) and at 12-32 month follow-up (53.1 vs. 45.8, P < .01). Computer navigation in TKA provides more accurate alignment and superior functional outcomes at short-term follow-up.

[Update on navigation in total knee arthroplasty. Where are we today and what lies in the future?]

BACKGROUND

The implantation of an artificial knee is one of the most common operative interventions in German hospitals. Navigation procedures have developed into an integral component of such interventions in the operating theatres of many clinics.

METHODS

For orthopedic surgeons who want to implement an as exact as possible reconstruction of the mechanical leg axis and require intraoperative control of the three dimensional positioning of components and/or the capsular ligament situation, navigation is a well-proven intraoperative tool. The immediate intraoperative control possibility of bone resection and capsular ligament soft tissue balancing means that navigation is a valuable instrument for the biomechanical fundamental understanding in training operations for further education of orthopedic surgeons in training.

DEVELOPMENTS

The greater precision obtained by the implementation of the procedure has not yet been conclusively reflected in an improved postoperative knee function or an increased durability of prostheses. New developments in navigated knee prostheses are pinless navigation and navigation kinematics. In pinless navigation the conventional reference marker system fixed in the femur and shin bones is replaced by a non-invasive reference system. With the aid of navigation kinematics it is possible to image the tibiofemoral and patellofemoral movement dynamics, intraoperatively.

PERSPECTIVE

The aim of the next generation navigation systems for computer-assisted knee prosthetics is implant positioning aligned to the individual anatomy of patients with high and stable range of movement for optimum patellar guidance and kinematics of the artificial joint.

Functional outcomes following total knee arthroplasty: a randomised trial comparing computer-assisted surgery with conventional techniques

BACKGROUND

A number of trials have shown improved radiological alignment following total knee arthroplasty using computer-assisted surgery (CAS) compared with conventional surgery. Few studies, however, have looked at functional outcomes.

METHODS

We prospectively studied a cohort of 107 patients that underwent TKA by a single surgeon. Patients were randomised into 3 groups: computer-assisted surgery for both the femur and the tibia, intramedullary guides for both the femur and the tibia, and an intramedullary guide for the femur and an extramedullary guide for the tibia. Patients were followed-up post-operatively with the Short Form Health Survey (SF-12) and Oxford Knee Score (OKS) questionnaires.

RESULTS

At a median follow-up of 46 months (range 30-69 months), there was a trend towards higher OKS results in the CAS group, with a mean score of 40.6 in the CAS group compared to 37.6 in the extramedullary group and 36.8 in the intramedullary group. The difference seen in the OKS between CAS and the conventional groups had a significant unadjusted p-value (0.024), and approached significance when adjusted for age and sex (0.054). There was a significant improvement in the OKS when the mechanical axis was within ±3° of neutral, versus those outside this range (median of 41.0 compared to 38.3, p=0.045).

DISCUSSION

This study shows that clinically significant differences are being seen in functional scores of patients treated with CAS versus conventional guides, at medium-term follow up. Our findings reinforce the tenet that a coronal mechanical axis of within 3° of neutral equates to significantly better functional outcomes.

Accuracy of a proximal tibial cutting method using the anterior tibial border in TKA

PURPOSE

In conventional total knee arthroplasty (TKA) using extramedullary alignment guides, it is not always easy to cut the proximal tibia precisely perpendicular to the tibial axis. The purpose of this study was to compare the radiographic accuracy of cutting the proximal tibia between the use of the bony landmarks of the anterior tibial border and the use of the conventional technique.

METHODS

A total of 173 patients underwent primary TKA. In 76 TKAs, we used the bony landmark method, and in 97 TKAs, we used the conventional method. In the bony landmark method, we set the coronal alignment in reference to the line connecting the proximal and distal one-third of the anterior tibial border, and we determined the 5° posterior slope in reference to this line. Six months postoperatively, radiological evaluations were performed using full-length standing anteroposterior and lateral radiographs of the knee.

RESULTS

No significant differences in the coronal tibial component angle were found between the groups. The posterior tilt of the tibial component was significantly smaller in the bony landmark method than in the conventional method (5.1° ± 2.9° vs. 6.4° ± 3.2°, respectively; p = 0.007). The percentage of patients whose posterior tilt of the tibial component was within ±3° of 5° was significantly larger in the bony landmark method than in the conventional method (70 vs. 62%, respectively; p = 0.04).

CONCLUSIONS

The bony landmark method provided a more accurate posterior tibial slope than the conventional method. However, there was no difference in coronal alignment compared with the conventional method.

Computer navigation and total knee arthroplasty

Research has added evidence in favor of computer-navigated techniques over conventional surgery for total knee arthroplasty (TKA). The goal of the current meta-analysis was to compare the outcome of outliers in mechanical axis and postoperative complications in patients undergoing conventional vs computer-navigated techniques for TKA. English literature searches were performed in PubMed, EMBASE, Web of Science, and the Cochrane Library for studies published between January 2002 and August 2012. Randomized, controlled trials comparing computer navigation with conventional surgery for the measurement of mechanical axes in patients with primary osteoarthritis were considered eligible. Fifteen trials were eligible for inclusion. The baseline demographics of 2089 patients (computer-navigated=1111; conventional=978) were well matched. Publication bias was eliminated using the funnel plot. A mechanical axis of more than 30° was considered to be malalignment and an outlier in limb alignment. A significant increase of 16.9 minutes in mean operative time for computer-navigated TKA was observed (P=.046). Although patients undergoing computer-navigated TKA had fewer outliers in mechanical axis (13.4%) compared with the conventional technique (27.4%), the results did not achieve statistical significance (I2=0.0%; P=1.000). Fewer complications were observed in patients undergoing computer-navigated TKA (4%) compared with conventional TKA (6.5%).

Clinical, functional, and radiographic outcomes following total knee arthroplasty with patient-specific instrumentation, computer-assisted surgery, and manual instrumentation: a short-term follow-up study

PURPOSE

The purpose of this study was to evaluate clinical, functional, and radiographic outcomes following total knee arthroplasty (TKA) performed with patient-specific instrumentation (PSI), computer-assisted surgery (CAS), and manual instruments at short-term follow-up.

METHODS

122 TKAs were performed by a single surgeon: 42 with PSI, 38 with CAS, and 40 with manual instrumentation. Preoperative, 1-month, and 6-month clinical and functional outcomes were measured using the Knee Society scoring system (knee score, function score, range of motion, and pain score). Improvements in clinical and functional outcomes from the preoperative to postoperative period were analyzed. Preoperative and postoperative radiographs were measured to evaluate limb and component alignment.

RESULTS

Preoperative, 1-month postoperative, and 6-month postoperative knee scores, function scores, range of motion, and pain scores were highest in the PSI group compared to CAS and manual instrumentation. At 6-month follow-up, PSI TKA was associated with a statistically significant improvement in functional score when compared to manual TKA. Otherwise, there were no statistically significant differences in improvements among PSI, CAS, and manual TKA groups.

CONCLUSION

The higher preoperative scores in the PSI group limits the ability to draw definitive conclusions from the raw postoperative scores, but analyzing the changes in scores revealed that PSI was associated with a statistically significant improvement in Knee Society Functional score at 6-month post-TKA as compared to CAS or manual TKA. This may be attributable to improvements in component rotation and positioning, improved component size accuracy, or other factors that are not discernible on plain radiograph.

Adjustable Slot Cutting Guide for Improved Accuracy During Bone Resection in Total Knee Arthroplasty

Slotted cutting guides are used by orthopaedic surgeons to improve the accuracy of bone resection during total knee replacement. Accuracy of the saw cuts has an effect on patient mobility and on implant survival time. While computer navigation systems have improved the accuracy of cutting guide placement, the contribution to cutting error from blade toggle within the slots of the cutting guide persists. In this research, equations were derived to quantify angular cutting error based on the parameters affecting blade and cutting guide geometry. Analytically, the relationship between cutting plane error and blade thickness was determined to be linear. A smaller gap, due to thicker blades with minimal tooth offset, results in less cutting error. From an experimental standpoint, six commercially available cutting guides were tested for femoral plane cutting accuracy by resection of synthetic bone under the guidance of computer navigation. The results indicate an average flexion/extension error of 3.8 deg for a 0.89 mm thick blade and 2.0 deg for a 1.27 mm blade. Varus/valgus error due to twisting of the blade within the slot was less than 1.0 deg, regardless of blade thickness. To improve upon cutting accuracy, an adjustable slot cutting guide was designed and tested. From more closely matching slot width to blade thickness, the results indicate that cutting plane error can be reduced to less than 1.0 deg in both the flexion/extension and varus/valgus planes.

Variations in ankle registration using two different anatomic landmarks: a radiographic study

PURPOSE

To quantify the average deviation in tibial mechanical axis registration when registering the ankle centre using (a) the extreme medial and lateral points and (b) the most distal points, of the respective malleoli, and to identify whether body mass index (BMI) had any significant effect on mechanical axis registration error.

METHODS

The preoperative standing hip-knee-ankle radiographs of 40 patients who underwent navigated TKR at our institution were reviewed. The divergence from the anatomic ankle centre in degrees and millimetres was compared when using the Extremes Midpoint and the Distal Midpoint techniques.

RESULTS

No significant divergence was measured with either the Extremes Midpoint (0.2° lateral, SD = 0.5°; 1.1 mm lateral, SD = 2.6 mm) or the Distal Midpoint (0.2° lateral, SD = 0.6°; 1.7 mm lateral, SD = 2.3 mm) techniques. BMI had no significant effect on these differences.

CONCLUSIONS

Both the Extremes Midpoint and the Distal Midpoint techniques offer accurate registration of the ankle centre. BMI does not seem to affect the registration of the ankle centre with either technique. The findings of this study will help knee surgeons when choosing an ankle registration technique. These results may also lead to more accurate knee replacement navigation systems.

Midterm outcomes of electromagnetic computer-assisted navigation in minimally invasive total knee arthroplasty

Background

A combination of two emerging technologies, computer-assisted navigation and minimally invasive surgery, in total knee arthroplasty has gained increasing interests from orthopedic surgeons around the world. To date, there has never been any midterm study for clinical and radiographic outcomes from using an electromagnetic computer-assisted navigation system. In this study, we aimed to systematically compare clinical and radiographic outcomes of minimally invasive surgery in total knee arthroplasty (MIS-TKA) performed with and without electromagnetic computer-assisted navigation at immediate and midterm follow-ups.

Methods

A total of 151 patients (160 knees) who underwent MIS-TKA were randomized to be operated with electromagnetic computer-assisted navigation (group I: 75 patients, 80 knees) or without the navigation (group II: 76 patients, 80 knees). The clinical and radiographic outcomes of immediate, 6-week postoperative follow-up and average 6.1-year follow-up were compared.

Results

On immediate, 6-week postoperative follow-up, clinical and radiographic outcomes did not reveal any difference between the two groups except for the fact that the operative time was longer in the navigation group. On 6.1-year follow-up, a total of 58 patients (63 knees) from group I and 58 patients (61 knees) from group II were reevaluated. There were no significant differences in clinical and radiographic loosening and in complications between the two groups.

Conclusion

In this study, no significant differences of clinical and radiographic outcomes were found for immediate and midterm follow-ups of MIS-TKA performed with and without electromagnetic computer-assisted navigation except for the additional operating time in the navigation group.

Joint line changes after primary total knee arthroplasty: navigated versus non-navigated

PURPOSE

Navigation has been introduced to achieve more accurate positioning of the implants after TKA. The scientific attention was mainly paid on limb alignment rather than restoration of the natural joint line. The aim of our study was to compare the accuracy of the joint line restoration in primary TKA with and without navigation. We hypothesized that joint line reconstruction in navigated TKA is more accurate.

METHODS

A total of 493 primary TKAs operated in a single medical centre were consecutively selected and divided into two groups. 206 cases were performed computer assisted (BrainLab CI-System), whereas 287 knees were implanted conventionally. For both groups, the joint line position of the knee was determined on standardized calibrated standing pre- and postoperative digital radiographs in ap view by a modified method of Kawamura et al. A joint line shift of more than 8 mm was defined as outlier.

RESULTS

In the conventional group, the joint line shift averaged 0.7 mm (±4.4 mm), whereas the findings in the computer-assisted cases were in average 0.6 mm (±4.5 mm). The joint line was located above 8 mm in 6 % of non-navigated versus 6.8 % of navigated primary TKAs. There were no statistically significant differences of joint line shift between the different component types. A statistically significant relation was not found between joint line shift and leg alignment changes.

CONCLUSIONS

Conventional surgical technique allows a precise joint line reconstruction in primary TKA. Navigation did not improve the joint line reconstruction.

LEVEL OF EVIDENCE

Diagnostic study, Level III.

A comparison of conventional and patient-specific instruments in total knee arthroplasty

PURPOSE

Several authors have observed that standard instrumentation (SI) may be insufficient for addressing component malalignment. Patient-matched cutting blocks (PMCB) technology was introduced to improve surgeons' ability to achieve a neutral postoperative mechanical axis following total knee arthroplasty (TKA). The current retrospective study was designed to compare the ability of SI and PMCB to achieve a hip-knee-ankle angle (HKA) within ±3° of the ideal alignment of 180°.

METHODS

Between October 2009 and December 2012, 170 TKAs in 166 patients (four bilateral) using VISIONAIRE (Smith & Nephew) PMCB technology were performed. Additionally, 160 TKAs in 160 consecutive patients that had received a total knee arthroplasty using SI during the same time period were used as a control group, All surgeries were performed by the same surgeon. Standardized pre- and postoperative long-leg standing x-rays were retrospectively evaluated to compare the two patient cohorts.

RESULTS

X-rays were available for analysis for 156 knees in the SI group and 150 in the PMCB group. The average post-surgical HKA was 178.7 ± 2.5 in the SI group and 178.4 ± 1.5 in the PMCB group. However, the rate of ± 3° outliers was 21.2 % in the SI group and 9.3 % in the PMCB group. There were no intraoperative complications with the use of PMCB technology or SI.

CONCLUSIONS

PMCB technology proved superior to conventional instrumentation in achieving a neutral mechanical axis following TKA. Further follow-up will be needed to ascertain the long-term impact of these findings.

Demonstration of saw blade accuracy and excursion: a cadaveric comparison study of blade types used in total knee arthroplasty

In total knee arthroplasty, outcomes partly depend on accurate osteotomies and integrity of stabilizing structures. We compared accuracy and excursion between a conventional and an oscillating tip saw blade. Two sets of osteotomies were made on cadaveric knees. Bi-planar accuracy was compared using computer navigation, and excursion was compared using methylene blue. Wilcoxon-Mann-Whitney testing demonstrated no significant difference in blade accuracy (p=0.35). Blades were within 0.5 degrees of neutral coronally and 2.0 degrees sagittally. The oscillating tip blade demonstrated less dye markings on the surrounding tissues. Accurate osteotomies and soft tissue protection are critical to successful arthroplasties. Although comparative accuracy was equal, the oscillating tip blade exhibited less excursion displaying potential for less iatrogenic soft tissue injuries leading to catastrophic failure.

Computer-assisted versus manual TKA: no difference in clinical or functional outcomes at 5-year follow-up

The purpose of this study was to determine whether differences in clinical, functional, or radiographic outcomes existed at 5-year follow-up between patients who underwent computer-assisted or manual total knee arthroplasty (TKA). Seventy-eight consecutive TKAs were performed by a single surgeon who had extensive experience performing computer-assisted and manual TKA. The manual group (n=40) and computer-assisted group (n=38) were similar with regard to age, sex, diagnosis, body mass index, surgical technique, implants, perioperative management, Knee Society scores, and anteroposterior mechanical axis. Sixty-three (manual group, n=34; computer-assisted group, n=29) patients were available for final follow-up. At 5-year follow-up, no statistically significant differences were found in Knee Society knee score (P=.289), function score (P=.272), range of motion (P=.284), pain score (P=.432), or UCLA activity score (P=.109) between the 2 groups. Postoperative radiographs showed a significant difference in the mechanical axis (P=.004) between the 2 groups; however, both groups achieved a neutral mechanical axis of ±3° (computer-assisted group mean, 2.0°; manual group mean, -0.24°).When TKA was performed by an experienced surgeon, no significant difference was identified at 5-year follow-up between patients who underwent computer-assisted vs manual TKA.

Columbus navigated TKA system: clinical and radiological results at a minimum of 5 years with survivorship analysis

The major factors that determine a favorable long-term clinical and functional outcome after conventional total knee arthroplasty (TKA) include correct implant positioning and restoration of the mechanical axis with soft tissue balancing to reduce aseptic failure; hence, the need for further developmental strategies that improve the accuracy and reproducibility of the surgical technique remains paramount for contemporary navigation research. Not all navigation systems are the same. The literature published thus far on mid-term results of navigated TKA relies on software that has no step-by-step soft tissue balancing with the tibia-first technique. The results are equivalent to those of conventional TKA.Therefore, the current authors conducted a minimum 5-year follow-up of a soft tissue-based navigated TKA system with the goal of soft tissue balancing. They analyzed intraoperative alignment and range of motion measurements, functional outcomes, radiographic assessment, and survival rates of high-flexion, high-conformity unresurfaced patella TKAs. The results at 5 years revealed a component revision rate of 0% compared with other nonnavigated TKAs (2.8% revision rate). The authors achieved a well-balanced TKA with a 0°±2° mechanical axis and an improved range of motion from 95° preoperatively to 110° postoperatively.

Evaluation of total knee arthroplasty performed with and without computer navigation: a bilateral total knee arthroplasty study

Sequential bilateral total knee arthroplasty performed on 54 patients utilizing navigation (CAS-TKA) in one knee and traditional instrumentation (T-TKA) in the contralateral knee was reviewed at a mean follow-up duration of 2.5years. There were no differences with regard to KSS, ROM, postoperative anatomic alignment, mechanical axis, or tibial angle. There was a statistically significant decrease in outliers for the CAS-TKA group with respect to anatomic alignment (3.7% vs. 17.0%, P=0.024), mechanical axis (6.1 vs. 20.4%, P=0.037) and tibial component alignment (0% vs. 7.5%, P=0.042). There is no apparent benefit of CAS-TKA with regards to KSS, ROM, or alignment in the hands of fellowship-trained total joint specialists. The clinical relevance of reduced outliers in the CAS-TKA group is unknown with the current follow-up interval.

Re-learning curve for conventional total knee arthroplasty following 30 consecutive computer-assisted total knee arthroplasties

A learning curve for returning to conventional total knee arthroplasty (TKA) after using computer-assisted (CAS) TKA has not yet been established. In this study, the postoperative mechanical axes of the first 30 consecutive CAS TKAs performed by a single surgeon were compared to his subsequent 120 conventionally performed TKAs. A "re-learning curve" of 30 conventional TKAs was necessary to attain an average postoperative mechanical axis statistically indistinguishable from the average CAS mechanical axis (1.99°). This is a trend of which surgeons should be aware when converting from CAS TKA to conventional TKA. As a secondary goal, the authors identify the first clinical parameter, preoperative deviation from neutral mechanical axis, that may potentially serve as a guide for the selective use of CAS in TKA.

Total knee arthroplasty with a computer-navigated saw: a pilot study

BACKGROUND

Computer-aided surgery aims to improve implant alignment in TKA but has only been adopted by a minority for routine use. A novel approach, navigated freehand bone cutting (NFC), is intended to achieve wider acceptance by eliminating the need for cumbersome, implant-specific mechanical jigs and avoiding the expense of navigation.

QUESTIONS/PURPOSES

We determined cutting time, surface quality, implant fit, and implant alignment after NFC of synthetic femoral specimens and the feasibility and alignment of a complete TKA performed with NFC technology in cadaveric specimens.

METHODS

Seven surgeons prepared six synthetic femoral specimens each, using our custom NFC system. Cutting times, quality of bone cuts, and implant fit and alignment were assessed quantitatively by CT surface scanning and computational measurements. Additionally, a single surgeon performed a complete TKA on two cadaveric specimens using the NFC system, with cutting time and implant alignment analyzed through plain radiographs and CT.

RESULTS

For the synthetic specimens, femoral coronal alignment was within ± 2° of neutral in 94% of the specimens. Sagittal alignment was within 0° to 5° of flexion in all specimens. Rotation was within ± 1° of the epicondylar axis in 97% of the specimens. The mean time to make cuts improved from 13 minutes for the first specimen to 9 minutes for the fourth specimen. TKA was performed in two cadaveric specimens without complications and implants were well aligned.

CONCLUSIONS

TKA is feasible with NFC, which eliminates the need for implant-specific instruments. We observed a fast learning curve.

CLINICAL RELEVANCE

NFC has the potential to improve TKA alignment, reduce operative time, and reduce the number of instruments in surgery. Fewer instruments and less sterilization could reduce costs associated with TKA.

Computer-assisted total knee arthroplasty is currently of no proven clinical benefit: a systematic review

BACKGROUND

Navigated total knee arthroplasty (TKA) may improve coronal alignment outliers; however, it is unclear whether navigated TKA improves the long-term clinical results of TKA.

QUESTIONS/PURPOSES

Does the literature contain evidence of better long-term function and lower revision rates with navigated TKA compared with conventional TKA?

METHODS

A systematic literature review was conducted of navigated TKA reviewing articles related to coronal alignment, clinical knee and function scores, cost, patient satisfaction, component rotation, anteroposterior and mediolateral stability, complications, and longer-term reports.

RESULTS

Coronal plane alignment is improved with navigated TKA with fewer radiographic outliers. We found limited evidence of improvements in any other variable, and function was not improved. The duration of surgery is increased and there are unique complications related to navigated TKA. The long-term benefits of additional increase in accuracy of alignment are not supported by any current evidence.

CONCLUSIONS

The findings in reports of navigated TKA should be interpreted with caution. There are few short- and medium- and no long-term studies demonstrating improved clinical outcomes using navigated TKA. Despite substantial research, contradictory findings coupled with reservations about the cost and efficacy of the technology have contributed to the failure of computer navigation to become the accepted standard in TKA. Longer-term studies demonstrating improved function, lower revision rates, and acceptable costs are required before navigated TKA may be widely adopted. In the future, with improvements in study design, methodology, imaging, navigation technology, newer functional outcome tools, and longer-term followup studies, we suspect that navigated TKA may demonstrate yet unrecognized benefits.

Component alignment and functional outcome following computer assisted and jig based total knee arthroplasty

BACKGROUND

Incorrect positioning of the implant and improper alignment of the limb following total knee arthroplasty (TKA) can lead to rapid implant wear, loosening, and suboptimal function. Studies suggest that alignment errors of > 3° are associated with rapid failure and less satisfactory function. Computer navigated systems have been developed to enhance precision in instrumentation during surgery. The aim of the study was to compare component alignment following computer assisted surgery (CAS) and jig based TKA as well as functional outcome.

MATERIALS AND METHODS

This is a prospective study of 100 knees to compare computer-assisted TKA and jig-based surgery in relation to femoral and tibial component alignment and functional outcome. The postoperative x-rays (anteroposterior and lateral) of the knee and CT scanogram from hip to foot were obtained. The coronal alignment of the femoral and tibial components and rotational alignment of femoral component was calculated. Knee society score at 24 months was used to assess the function.

RESULTS

Results of our study show that mean placement of the tibial component in coronal plane (91.3037°) and sagittal planes (3.6058°) was significantly better with CAS. The difference was statistically insignificant in case of mean coronal alignment of the femoral components (90.34210° in navigation group and 90.5444° in jig group) and in case of the mean femoral condylar twist angle (external rotation 2.3406° in navigation group versus 2.3593° in jig group).

CONCLUSIONS

A significantly improved placement of the component was found in the coronal and sagittal planes of the tibial component by CAS. The placement of the components in the other planes was comparable with the values recorded in the jig-based surgery group. Functional outcome was not significantly different.

Computer-assisted total knee arthroplasty for significant tibial deformities

Computer-assisted total knee arthroplasty has been demonstrated to provide reproducible limb mechanical alignment within 3° from the neutral mechanical axis. However, restoring proper implant and extremity alignment remains a significant challenge with proximal tibial deficiencies. In this prospective study, we describe the use of computer navigation to quantify the amount of bone loss on the medial or lateral tibial plateau and the use of these data to assess the need for augmentation with metallic tibial wedges. In this study, we demonstrate that computer-assisted total knee arthroplasty in patients with significant tibial deformities can accurately measure severe tibial deformities, predict tibial augment thickness, and provide excellent mechanical alignment and restore the joint line without excessive bony resection, repeated osteotomies, and repeated augment trialing.

A vascular complication in computer navigated total knee arthroplasty

The use of computer navigation has the potential to improve implant position in total knee arthroplasty (TKA), but pin fixation of reference arrays introduces an additional potential source of complications. We report a case of vascular injury related to the insertion of a femoral pin during navigated TKA.

Customization of cutting blocks: Can this address the problem?

Recent literature has challenged the notion that neutral coronal alignment is a requirement for long-term survivorship of TKAs. However a preponderance of classic and contemporary evidence supports increased failure rates with malalignment, especially varus. Patient-specific custom cutting guides are an attractive alternative to traditional instrumentation and computer navigation in achieving accurate alignment of total knee arthroplasties. The logistical benefits include possible decreased operating room time, decreased turnover time, less time spent sterilizing and preparing trays, less inventory, less strain on surgical technicians and nurses, and no capital cost associated with computer navigation. Patient benefits include potentially less tourniquet time, less surgical exposure, no requirement of intramedullary canal preparation, and improved mechanical alignment, which may translate to increased implant longevity. Surgeon benefits include potentially more accurate landmark registration than computer navigation, more efficient surgery, decreased intraoperative stress due to less required decision making, and the ability to perform more surgeries due to time saved.

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.

Computer assisted versus conventional total knee replacement: a comparison of tourniquet time, blood loss and length of stay

AIMS AND INTRODUCTION: The aim of this study was to assess whether navigated total knee arthroplasty (TKA) reduces peri-operative blood loss and post-operative length of stay when compared to conventional total knee arthroplasty techniques.

PATIENTS AND METHODS

A retrospective case-note review of 143 patients undergoing primary elective total knee arthroplasty was carried out. Two surgeons in this institution perform conventional knee arthroplasty using intramedullary alignment with another two surgeons using the computer assisted technique. Blood losses were calculated using the Meunier et al. (2008) [23] method for calculation of peri-operative blood loss. This is based on changes in peri-operative blood indices compared to the patient's theoretical total blood volume which is calculated using the patient's pre-operative height and weight. Tourniquet time and post-operative length of stay for the two techniques of arthroplasty were also recorded.

RESULTS

Sixty eight patients underwent conventional TKA and 75 patients had navigated TKA's performed. This data showed no significant difference in blood loss (p=0.56) or post-operative length of stay (p=0.36). A significant difference in tourniquet time between the two techniques was demonstrated (p=0.01).

CONCLUSION

In this study there was no significant reduction in post-operative length of stay and peri-operative blood loss when using computer-assisted techniques. There was an increase in tourniquet time with the computer-assisted technique that may have implications upon work productivity for primary cemented knee arthroplasty.

Coronal alignment correlates with outcome after total knee arthroplasty: five-year follow-up of a randomized controlled trial

In a prospective randomized control trial comparing computer-assisted vs conventional total knee arthroplasty, we previously reported that patients with coronal alignment within 3° of neutral had superior international knee society and Short-Form 12 (SF-12) physical scores at 6 weeks, 3 months, 6 months, and 12 months after surgery. Computer-assisted total knee arthroplasty achieved greater accuracy in implant alignment, and this correlated with better knee function and quality of life. At 5 years, 90 of 111 patients assessed in our original study were reviewed. Coronal alignment within 3° of neutral continued to be correlated with superior International Knee Society and SF-12 scores. Coronal alignment greater than 3° was associated with a significant decline in SF-12 mental health scores.

Systematic review of computer-navigated total knee arthroplasty

BACKGROUND

Conventional total knee arthroplasty (TKA) and the more recently available computer-navigated total knee arthroplasty (CNTKA) use alternative methods to achieve correct limb alignment. This systematic review was undertaken to assess the safety and effectiveness of CNTKA compared with conventional TKA.

METHODS

A systematic search of multiple databases identified relevant randomized controlled trials published to August 2012. Study inclusion was established through application of a predetermined protocol, with independent assessment by two reviewers.

RESULTS

Thirty randomized controlled trials were included. The majority of adverse events associated with CNTKA were minor and comparable with those seen with conventional TKA. Conversion to conventional TKA was required in 1% of patients undergoing CNTKA. Thirteen trials reporting on satisfactory post-operative radiological alignment of the mechanical axis in the frontal plane were suitable for meta-analysis, which showed a significant total odds ratio (non-event) of 2.32 (95% confidence interval: 1.77-3.04) in favour of CNTKA (P < 0.00001). Clinical outcomes were comparable between the two techniques, with longer-term follow-up suggesting that CNTKA provided no benefit over conventional TKA in terms of sustained functional improvements.

CONCLUSIONS

At present, it is unclear whether the significant improvements shown in radiological outcomes after CNTKA translate to measurable clinical benefits. Although an assumption could be made that an improvement in post-operative alignment should lead to an improvement in patient-related outcomes, the available literature did not clearly show this. Further, long-term trials are required to address this issue.

Little clinical advantage of computer-assisted navigation over conventional instrumentation in primary total knee arthroplasty at early follow-up

PURPOSE

Even though computer-assisted navigation systems have been shown to improve the accuracy of implantation of components into the femur and tibia, long-term results are lacking and there is little evidence yet that navigation techniques also improve functional outcomes and implant longevity following total knee arthroplasty (TKA). The aim of this study was to summarize and compare the clinical outcomes of total knee arthroplasties (TKAs) performed using navigation-assisted and conventional techniques.

METHODS

The study was conducted according to the guidelines described in the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statements. Methodological features were rated independently by two reviewers. A meta-analysis of randomized controlled trials (RCTs) or quasi- randomized controlled trials (qRCTs) was carried out to evaluate the efficacy of CAS versus conventional TKA. Data were pooled in fixed and random effects models and the weighted mean difference (WMD) and odds ratio (OR) were calculated. Heterogeneity across studies was determined, and subgroup analyses by the type of navigation system (image-based or image-free navigation system) were conducted.

RESULTS

Twenty-one studies that included 2333 knees were collected from different countries. The surgical time was longer for CN TKA than for the conventional procedure. There was no significant difference in the Knee Society Score between the two groups at the 3-month and 6-month follow-up. The rates of postoperative complications in patients who had CN TKA were similar to those in the patients who had conventional TKA.

CONCLUSION

No significant differences in short-term clinical outcomes were found following TKAs performed with and without computer navigation system. However, there is clearly a need for additional high-quality clinical trials with long-term follow-up to confirm the clinical benefits of computer-assisted surgery.

Computer-assisted navigation in high tibial osteotomy: a systematic review of the literature

High tibial osteotomy (HTO) is a procedure which aims to change the mechanical axis of the lower limb, transferring the body weight across healthy articular cartilage. Several studies have shown that accurate correction is the leading predictor for success.

In this article, we systematically review the computer-assisted techniques that have been used in attempts to increase the accuracy of the surgery and improve postoperative outcomes. The results of the cadaveric and clinical studies to date are presented and the benefits and pitfalls of navigation are discussed.

Does computer-assisted surgery improve postoperative leg alignment and implant positioning following total knee arthroplasty? A meta-analysis of randomized controlled trials?

PURPOSE

Computer-assisted surgery has been proposed as a technique to improve implant alignment during total knee arthroplasty (TKA). However, there is still a debate over the accuracy of placing the femoral and tibial components using computer-assisted systems in TKA. The aim of this study is to establish whether computer-assisted surgery leads to superior mechanical leg axis and implant positioning than conventional technique in patients with primary TKA.

METHODS

Major electronic databases were systematically searched to identify relevant studies without language restriction. A meta-analysis of 41 randomized controlled trials (RCTs) or quasi-RCTs was performed in a random effects model. A subgroup analysis was conducted by type of navigation system to explore the clinical heterogeneity between these trials. The following radiographic parameters were used to compare computer-assisted surgery with conventional technique: (1) mechanical leg axis, (2) femoral component coronal alignment, (3) tibial component coronal alignment, (4) femoral component sagittal alignment, and (5) tibial component sagittal alignment.

RESULTS

For the mechanical leg axis and coronal positioning of femoral and tibial components, there are statistically significant reductions in the number of patients with malalignment in the CAS group if the outlier cutoff value is ±3 or 2° in the coronal and sagittal planes, respectively. Subgroup analysis demonstrates that CT-free navigation systems provide better alignment than conventional techniques in the coronal and sagittal alignment of femoral components within ±3 and 2°. If the outlier cutoff value for the tibial sagittal alignment is ±2°, the outlier percentages are higher in the CT-free navigation group than in the conventional group. However, there was no significant difference in the tibial sagittal alignment at ±3°.

CONCLUSION

Computer-assisted surgery does improve mechanical leg axis and component orientation in TKAs. However, high-quality RCTs are necessary to determine whether surgeons could use computer-assisted techniques to achieve a targeted tibial slope in TKA.

LEVEL OF EVIDENCE

Therapeutic study (Systematic review of Level I/II studies), Level II.

Custom-fit total knee arthroplasty: our initial experience in 32 knees

We share our initial experience of total knee arthroplasty (TKA) using customized cutting block technology in 32 TKAs from May 2010 to March 2011. Ten of these patients had prior TKA done on the other side using conventional or navigation-assisted TKA. Customized cutting blocks were generated for each of the knee using preoperative magnetic resonance imaging of knee and long-leg weight-bearing radiographs. At 6 weeks, long-leg radiographs were obtained to evaluate the coronal alignment. There were no adverse intraoperative events. Twenty-nine of the 32 knees had a mechanical axis restored to within 3°° of neutral. Of 10 patients with prior TKA without custom-fit technology, the mean blood loss and the mean skin-to-skin time was found to be lower in knees that had undergone custom-fit TKA. We conclude that this technology can be safely used in most of the cases of osteoarthritis.

Alignment outcomes in navigated total knee arthroplasty: a meta-analysis

PURPOSE

Whether navigated total knee arthroplasty can improve the limb and component alignment is a matter of debate. This systematic literature review analyzed the differences on alignment outcomes between navigated total knee arthroplasty and conventional total knee arthroplasty.

METHODS

Multiple databases, online registers of randomized controlled trials were searched. Published and unpublished randomized controlled trials were included, and data on methodological quality, population, intervention, and outcomes were abstracted in duplicate. Data were pooled across studies, and odds ratios for categorical outcomes were calculated according to study sample size.

RESULTS

Twenty-one randomized controlled trials of varying methodological quality involving 2,414 patients were included. Statistically significant differences were observed between navigated group and conventional group in mechanical axis malalignment of >3° (odds ratio, 0.26; 95% confidence interval, 0.17-0.38) and mechanical axis malalignment of >2° (odds ratio, 0.33; 95% confidence interval, 0.26-0.42). Navigated group had a lower risk of malalignment for both coronal femoral component and coronal tibial component of >3° and >2°. Both sagittal femoral component alignment and tibial slope showed statistical significance in favor of navigated arthroplasty at >2° and 3° malalignment.

CONCLUSION

Meta-analysis indicates significant improvement in alignment of the limb and the component position with use of computer navigation system. Its clinical benefits are unclear and remain to be defined on a larger scale randomized controlled trials with long-term follow-up.

LEVEL OF EVIDENCE

Therapeutic study (Systematic review of Level-I studies with inconsistent results), Level II.

Meta-analysis of navigation vs conventional total knee arthroplasty

Navigated total knee arthroplasty (TKA) is promoted as a means to improve limb and prosthesis alignment. This study involved a systematic review and meta-analysis for all randomized controlled trials in the literature from 1986 to 2009 comparing alignment outcomes between navigated and conventional TKA. Alignment outcomes were pooled using a random-effects model, and heterogeneity was explored. Twenty-three randomized controlled trials were identified comparing navigated vs conventional TKA involving 2541 patients. Patients who underwent navigated TKA had a significantly lower risk of implant malalignment at more than 3° as well as more than 2°. In addition, the risk of malalignment was reduced for the coronal plane tibial and femoral components as well as femoral and tibial slope. This meta-analysis demonstrates that navigated TKA provides significant improvement in prosthesis alignment.

Navigated cementless total knee arthroplasty - medium-term clinical and radiological results

Purpose:

The objective of this prospective study was to evaluate the medium-term clinical and radiological results after navigated cementless implantation, without patella resurfacing, of a total knee endoprosthesis with tibial and femoral press-fit components, with a focus on survival rate and clinical outcome. The innovation is the non-cemented fixation together with the use of a navigation system.

Scope and Methods:

Sixty patients with gonarthrosis were included consecutively in this study. In all cases, the cementless Columbus total knee endoprosthesis with a coating out of pure titanium was implanted, using a navigation system. The Knee Society Score showed a statistically significant increase from 75 (± 21.26) before surgery to 180 (± 16.15) after a mean follow-up of 5.6 (± 0.25) years. The last radiological examination revealed no osteolysis. No radiolucent lines were seen at any time in the area of the femoral prosthetic components. In the tibial area, radiolucent lines were seen in 24.4 % of the cases, mostly in the distal uncoated part of the stem. During follow-up, no prosthesis had to be replaced because of aseptic loosening while in 2 cases revision surgery was necessary due to septic loosening and in 1 case due to unexplainable pain.

Results and Conclusions:

Navigated cementless implantation of the Columbus total knee endoprosthesis yielded good clinical and radiological results in the medium term. The excellent radiological osteointegration of the prosthetic components, coated with a microporous pure titanium layer and implanted with a press-fit technique, should be emphasized.

Computer navigation vs conventional total knee arthroplasty: five-year functional results of a prospective randomized trial

Seventy-one patients were randomly allocated to undergo either computer-navigated or conventional arthroplasty. A statistically significant improvement in alignment was seen in the computer-navigated cohort. Five-year functional outcome was assessed using the Knee Society, Short Form-36, Western Ontario and McMaster Universities Osteoarthritis Index, and a patient satisfaction score. At 5 years, 46 patients were available for assessment (24 navigated and 22 conventional knees). No patients had undergone revision. No statistically significant difference was seen in any component of any measure of outcome between navigated and conventional cohorts. Longitudinal data showed function to be well maintained with no difference in functional score between 2 and 5 years in either cohort. Despite achieving better alignment, 5 years postoperatively, the functional outcome with computer-navigated knee arthroplasty appears to be no different to that implanted using a conventional jig-based technique.

Clinical Outcomes After Computer-assisted Versus Conventional Total Knee Arthroplasty

The purpose of this study was to determine whether the use of computer-assisted surgery can improve the clinical results in total knee arthroplasty (TKA) compared with conventional methods of TKA.A literature search of PubMed (1966 to August 2011), CENTRAL (Cochrane Controlled Trials Register; issue 3, 2011), and EMBASE (1984 to August 2011) was conducted. Randomized, controlled trials detecting the clinical outcomes of TKA with or without the use of computer-assisted surgery were identified. A meta-analysis of these clinical trials was then performed. Twenty-one articles were included in the meta-analysis. The results confirmed that operative time was significantly increased with the use of computer-assisted TKA (mean standard difference, 14.68; 95% confidence interval [CI], 11.74 to 17.62; P<.00001], whereas no significant difference existed between the 2 groups regarding the total operative blood loss (mean standard difference, -54.38; 95% CI, -119.76 to 11.00; P=.10). As for other clinical outcomes, including the Knee Society Score (mean standard difference, 4.47; 95% CI, -1.05 to 9.99; P=.36) and range of motion (mean standard difference, 1.38; 95% CI, -1.43 to 4.18; P=.34), the use of computer-assisted TKA did not help to improve function recovery postoperatively.

Computer navigation vs extramedullary guide for sagittal alignment of tibial components: radiographic study and meta-analysis

Sagittal alignment of tibial components using computer navigation was compared with conventional methods. A radiologic study was performed using 110 total knee arthroplasties from 3 groups: computer navigation, cutting block with extramedullary guide, and manual tilt of extramedullary guide. Posterior tibial slopes were measured from radiographs and compared using statistical methods. The cutting block method was the most accurate, and computer navigation was the most precise. The manual tilt group had the greatest variance, significantly greater than computer navigation. There was no significant difference between groups with respect to the percentage of knees with posterior slope within 3° of the desired slope. Meta-analysis of 10 studies found no reduction in outliers with computer navigation. Computer navigation offers greatest precision but does not reduce the number of outliers.

Precision of Ci-navigated extension and flexion gap balancing in total knee arthroplasty and analysis of potential predictive variables

INTRODUCTION

The aim of this study was to evaluate the accuracy of final limb alignment and flexion-extension and medial-lateral gap balancing in computer navigated total knee arthroplasty and to analyze various possible predictive variables that may affect the gaps in computer navigated knee arthroplasty.

MATERIALS AND METHODS

The DePuy Ci system, a nonimage-based passive optical computer navigation system, was used in 225 patients with knee osteoarthritis to assist for the total knee arthroplasty. From the raw data the Ci-verified pre- and postoperative leg axis in extension, angle of tibia and femur resection, the flexion and extension angle, the medial and lateral extension and flexion gaps were extracted; and differences in gaps were calculated and subjected to statistical analysis. Leg alignment and implant position were determined only by the navigation system. Preoperative variables were evaluated for their impact on the final flexion/extension and medial/lateral gaps achieved.

RESULTS

Though the preoperative femoro-tibial coronal alignment had a large variance, postoperatively 98.22% of the knee was found to be between -3° and +3° in the coronal limb alignment axis. The Ci-verified femoral and tibial cuts in the coronal plane showed a good accuracy. The sagittal alignment of the femoral cut ranged from 8.20° flexion to 3.20° of extension. Rectangular extension and flexion gaps were achieved with ≤3 mm of difference in gaps on medial and lateral sides in 98 and 93% of knees, respectively. Difference between extension and flexion gaps on the medial side was ≤3 mm in 83% and on the lateral side in 84% of the knees. Of all the possible predictive variables analyzed, Pearson correlation and multiple regression analysis showed significant correlation only between the medial-lateral gap difference in extension and the Ci-verified femoral cut, tibial cut and limb axis, all in the coronal plane.

CONCLUSION

Computer-assisted navigated total knee replacement allows for accurate gap balancing that is not dependent on the various pre- and intraoperative factors mentioned, including age, sex, Range of motion preoperative deformity and grade of osteoarthritis. The Ci-calculated and verified tibial, and femoral cuts are the only possible factors affecting the extension gap.

Patient-specific instrumentation for total knee replacement verified by computer navigation: a case report

Patient-specific instrumentation (PSI) enables better restoration of the mechanical axis in total knee replacement (TKR) than conventional instrumentation (alignment guides) does. We verified the accuracy of the PSI by computer navigation. The PSI jigs were accurate only if they were pinned accurately onto the distal femur and proximal tibia. Any slight malposition of the jigs leads to malalignment of the bone cuts. In the absence of computer navigation, the accuracy of the jig alignments cannot be checked and may result in malalignment.

Natural distribution of the femoral mechanical-anatomical angle in an osteoarthritic population and its relevance to total knee arthroplasty

A common surgical goal in TKA is to restore neutral alignment of the lower limb by making bone cuts perpendicular to the mechanical axes of the femur and tibia. Standard practice for many surgeons is to use the same distal femoral valgus resection angle for all patients, assuming little or no variation in the femoral mechanical-anatomical (FMA) angle between different patients' knees. This study analysed 174 pre-operative hip-knee-ankle radiographs of osteoarthritic knees (157 patients, 87 female and 70 male, mean age 70years and mean BMI 31.8). Measurements of mechanical femorotibial (MFT) and FMA angles were made. The mean FMA angle was 5.7° (SD 1.2°, range 2° to 9°). There was a statistically significant difference between the FMA angle for males and females with males tending to have larger FMA angles (p<0.001). There was a statistically significant correlation between MFT and FMA angle (r=-0.499) with varus knees tending to have larger FMA angles (p<0.001). These results indicate a wide distribution of FMA angle in an osteoarthritic population. In terms of achieving appropriate coronal alignment in TKA the use of a fixed valgus resection angle is not suitable for all patients and it may be preferable to adjust the distal femoral cut according to individual FMA angles. However if this angle is not available the cut may be adjusted according to pre-operative coronal alignment, using 6° for neutral/mild varus, >6° for more severe varus and <6° for valgus knees.

Joint line is well restored when navigation surgery is performed for total knee arthroplasty

PURPOSE

The incorrect restoration of the joint line during TKA can result in joint instability, anterior knee pain, limited range of motion, and joint stiffness. The joint line level is usually measured only on pre- and post-operative radiographs. Current knee navigation systems can now potentially support intra-operatively joint line restoration by controlling the exact amount of the bone-cartilage removed and the corresponding overall thickness of the components implanted. The aim of this study was to assess how well the joint line level is restored and the tibiofemoral overstuffing prevented when standard knee surgical navigation is used carefully also with these purposes. Intra-operative measurements during navigated TKA were taken.

METHODS

Sixty-seven primary TKAs were followed prospectively. The variation before and after prosthesis component implantation of the joint line level, both in the femoral and tibial reference, was measured intra-operatively by an instrumented probe. Overstuffing was measured as the difference between the overall craniocaudal thickness of the femoral and tibial prosthesis components inserted and the thickness of the bone-cartilage removed.

RESULTS

A significant elevation in the joint line level after prosthesis implantation was found with respect to the tibial reference (1.9 ± 2.4 mm, mean ± SD), very little to the femoral reference (0.3 ± 2.1 mm), perhaps accounted for the femur-first operative technique utilized. Overstuffing was on the average of 2.2 ± 3.0 mm.

CONCLUSIONS

These results suggest that a knee navigation system can also support well a proper restoration of the joint line level and limit the risk of overstuffing when relevant measurements are taken carefully during operation.

LEVEL OF EVIDENCE

III.

Novel patient-specific navigational template for total knee arthroplasty

Current techniques for total knee arthroplasty have certain drawbacks, including violation of the intramedullary canals and limited accuracy. The aim of this research was to develop and validate the accuracy of a new computer-assisted preoperative planning concept for the creation of patient-specific navigational templates to replace conventional instruments. Volumetric computerized tomography (CT) scanning was performed on 30 cadaveric knees, and a three-dimensional reconstruction model of each knee was generated from the scan data. Using a reverse-engineering technique, optimal lower-limb alignment and rotational alignment were determined. A navigational template was also designed with a surface that matched the distal femur and proximal tibia. This template, with its corresponding femur and tibia, was manufactured using a rapid-prototyping technique and tested for violations. The navigational template was then used intraoperatively to assist with an arthroplasty in each of the 30 cadaveric knees. Following surgery, the positions of the prostheses were evaluated with X-rays and CT scans. The method showed a high degree of accuracy and reproducibility. In all cases, placing the template manually on the lamina of the femur and tibia was relatively easy. Twenty-eight prostheses were considered to be positioned entirely accurately, whereas two prostheses were considered to have a 1-2° malpositioning. This study thus introduces a novel navigational template for total knee arthroplasty. Preliminary cadaveric trials have demonstrated that this design can improve the accuracy of osteotomy in the surgical procedure.

Navigation in minimally invasive unicompartmental knee arthroplasty has no advantage in comparison to a conventional minimally invasive implantation

INTRODUCTION

Minimally invasive implantation of unicompartmental knee prostheses can shorten rehabilitation time and lead to better functional results than conventional implantation. Exact positioning of the implant should be achieved, as this is a factor for the long-term survival of the prosthesis, although malpositioning can result due to the poor intraoperative view when using the minimally invasive approach. Navigation of the unicompartmental prosthesis could lead to a better implant positioning without losing the advantages of a minimally invasive approach.

MATERIALS AND METHODS

The same unicondylar knee prosthesis was implanted in a total of 40 patients, of whom 20 were implanted using navigation (kinematic navigation) and 20 using a conventional technique. The operating time was assessed in both groups. The orientation of the tibial and femoral implants was assessed radiologically postoperatively. We analysed these results according to the optimal positioning range proposed by the manufacturer. Furthermore, we examined the clinical results with the knee society score (KSS).

RESULTS

A good positioning of the prosthesis was observed in both techniques with only 11% of the radiologic measurements out of the proposed optimal range in each group. The operating time was significantly longer in the navigation group (17 min). The KSS did not differ between both groups at a follow-up of 16 resp. 18 months (navigated group: 184 points, conventional group: 178 points).

CONCLUSIONS

Navigation did not lead to a better positioning of the prosthesis than the conventional method and the operating time was longer. The clinical results were similar in both groups. The navigation may be a useful help for surgeons performing less unicompartmental knee arthroplasty using a minimally invasive approach.

Assessing short-term functional outcomes and knee alignment of computer-assisted navigated total knee arthroplasty

This retrospective study examined the relationship between the mechanical axis of the knee throughout its functional arc and functional outcomes in patients with computer-assisted navigation total knee arthroplasty. Data on final intraoperative functional arc alignment were obtained on 76 patients who had computer-assisted navigation total knee arthroplasty over a 2-year period and correlated with scores from postoperative Short Form 12 and Western Ontario and McMaster Universities functional outcome surveys. No correlation was found between functional arc alignment and outcomes from Western Ontario and McMaster Universities or Short Form 12 surveys; however, subgroup analysis of patients with more than 3° average final intraoperative alignment throughout the functional arc of motion demonstrated increased difficulty with daily activities (P = .05). The results indicate that patients with more than 3° average alignment throughout the functional arc of motion perform more poorly with daily activities postoperatively.

Recent advances in reconstructive oral and maxillofacial surgery

Reconstruction within the head and neck is challenging. Defects can be anatomically complex and may already be compromised by scarring, inflammation, and infection. Tissue grafts and vascularised flaps (either pedicled or free) bring healthy tissue to a compromised wound for optimal healing and are the current gold standard for the repair of such defects, but disadvantages are their limited availability, the difficulty of shaping the flap to fit the defect and, most importantly, donor site morbidity. The importance of function and aesthetics has driven advances in the accuracy of surgical techniques. We discuss current advances in reconstruction within oral and maxillofacial surgery. Developments in navigation, three-dimensional imaging, stereolithographic models, and the use of custom-made implants can aid and improve the accuracy of existing reconstructive methods. Robotic surgery, which does not modify existing techniques of reconstruction, allows access, resection of tumours, and reconstruction with conventional free flap techniques in the oropharynx without the need for mandibulotomy. Tissue engineering and distraction osteogenesis avoid the need for autologous tissue transfer and can therefore be seen as more conservative methods of reconstruction. Recently, facial allotransplantation has allowed whole anatomical facial units to be replaced with the possibility of sensory recovery and reanimation being completed in a single procedure. However, patients who have facial allotransplants are subject to life-long immunosuppression so this method of reconstruction should be limited to selected cases.

Three-dimensional component alignment and functional outcome in computer-navigated total knee arthroplasty: a prospective, randomized study comparing two navigation systems

Computer navigation in total knee arthroplasty produces better component alignment than conventional techniques. Different navigation systems exist. We undertook a prospective, randomized study comparing 2 navigations systems (Stryker Full Navigation and Stryker Articular Surface Mounted [ASM] navigation systems). Three-dimensional component alignment (Perth computed tomographic knee protocol) and function at 1 year (Knee Society Scores) were assessed. Forty patients participated (20 fully navigated and 20 ASM-navigated total knee arthroplasties). Cohorts were well matched according to sex, age, and body mass index. No statistically significant difference was seen in any parameter of 3-dimensional component alignment or function between cohorts. Operative time for the ASM cohort was significantly less than the fully navigated cohort (P = .001). Both systems performed equally well, and therefore, surgeon preference should determine which system is used.

Computer assisted navigation in knee arthroplasty

Computer assisted surgery (CAS) was used to improve the positioning of implants during total knee arthroplasty (TKA). Most studies have reported that computer assisted navigation reduced the outliers of alignment and component malpositioning. However, additional sophisticated studies are necessary to determine if the improvement of alignment will improve long-term clinical results and increase the survival rate of the implant. Knowledge of CAS-TKA technology and understanding the advantages and limitations of navigation are crucial to the successful application of the CAS technique in TKA. In this article, we review the components of navigation, classification of the system, surgical method, potential error, clinical results, advantages, and disadvantages.

Comparison of joint line position changes after primary bilateral total knee arthroplasty performed using the navigation-assisted measured gap resection or gap balancing techniques

PURPOSE

This study aimed to compare the clinical and radiological results of navigation-assisted TKAs performed using the measured gap resection or the gap balancing technique in thirty patients who underwent bilateral primary TKAs.

METHODS

Sixty cases of navigation-assisted TKAs [30 TKAs performed using the measured gap resection technique (Group A) and 30 TKAs performed using the gap balancing technique (Group B)] were analyzed prospectively with minimum follow-up of 2 years. The joint line positions were measured using preoperative and postoperative weight-bearing anteroposterior and lateral radiographs. Clinical results were evaluated using knee scores and functional scores.

RESULTS

No significant differences in knee scores or functional scores were observed. Polyethylene thickness and flexion/extension gaps were significantly larger in Group B (P < 0.05). The meaningful proximal shift of the joint line was shown in Group B (P < 0.05).

CONCLUSION

The navigation-assisted TKA with measured gap resection technique could be a useful technique with regard to restoration of the joint line.

Randomized trial of computer-assisted knee arthroplasty: impact on clinical and radiographic outcomes

Computer-assisted surgery in knee arthroplasty is gaining popularity; however, the resulting outcome improvement is controversial. A double-blinded trial was performed with subjects randomized to undergo surgery with either computer-assisted or nonassisted instruments. Postoperatively, limb and implant alignment and rotation were assessed using both full-length radiographs and computed tomography in addition to clinical scores. One hundred twenty patients (141 knees) were randomized. No differences in Western Ontario MacMaster Osteoarthritis Score, Short Form-36, or flexion were seen. More varus limb alignment was seen in the computer-assisted group (1.9°) vs the nonassisted group (0.9°, P = .04) with no improvement in alignment precision. Rotational alignment of the components did not differ between groups. Computer-assisted surgery appeared to have minimal effect on knee implant arthroplasty with no improvement in limb alignment or early functional outcome.