Navigated total knee replacement. A meta-analysis

Electromagnetic navigation in total knee arthroplasty-a single center, randomized, single-blind study comparing the results with conventional techniques

We report on the results of a randomized study (n=200) to compare total knee arthroplasty performed using conventional instrumentation or electromagnetic computer assisted surgical technique. 92% of navigated and 85% of conventional knees were implanted within ±3° from neutral mechanical alignment; there was no statistically significant difference between these proportions. There was also no difference in femoral or tibial rotation assessed by CT scan. At 1year follow up there was no statistical difference between the two groups in American Knee Society Score, Oxford Knee Scores, patient satisfaction, quality of life, hospital length of stay, complication rates or other adverse events. Tourniquet time in the navigated group was longer. Proving value for navigation in total knee arthroplasty surgery remains a challenge.

Benefit of intraoperative navigation on glenoid component positioning during total shoulder arthroplasty

INTRODUCTION

The objective of this study was to review and synthesize the current best evidence for the use of intraoperative navigation in the implantation of glenoid components in total shoulder prostheses.

METHODS

We conducted a systematic, online search using PubMed, EMBASE, CCTR, and CINAHL using "Arthroplasty, Replacement"(Mesh) AND (shoulder) AND (navi* OR computer). Data on study design and quality as well as accuracy of positioning and complications were extracted independently and in duplicate. After assessment of study heterogeneity, DerSimonian-Laird random effect models were used to pool data from the individual studies.

RESULTS

The systematic search revealed 359 manuscripts in total. After exclusion of duplicates and irrelevant publications, 6 groups of 247 shoulders from 5 studies were included. The pooled weighted mean difference for deviation from neutral version was -6.4° (95 %CI -7.9 to -5.3) in favor of navigation, which is consistent with a statistically significant difference (p < 0.01). In the navigation group, 2 superior glenoid screws were reported as perforating compared to 5 screws (1 inferior, 4 superior) in the control group. There was no difference in tilt at a WMD of 2.7 (95 %CI -1.4 to 6.8, p = 0.192).

CONCLUSIONS

Navigation allows for significantly more accurate glenoid version, but the clinical meaningfulness of the absolute improvement over standard techniques is questionable. However, navigation is a valuable teaching tool that might prove very beneficial not for the patient at hand, but for those treated by the operating surgeon in the future.

LEVEL OF EVIDENCE

Level II-meta-analysis of non-homogenous controlled trials.

Improved alignment and operating room efficiency with patient-specific instrumentation for TKA

BACKGROUND

Achieving accurate alignment in total knee arthroplasty (TKA) remains a concern. Patient-specific instrumentation (PSI) produced using preoperative 3D models was developed to offer surgeons a simplified, reliable, efficient and customised TKA procedure.

METHODS

In this prospective study, 60 patients underwent TKA with conventional instrumentation and 71 patients were operated on using PSI. The primary endpoint was surgical time. Secondary endpoints included operating room (OR) time, the number of instrument trays used and postoperative radiographic limb alignment.

RESULTS

Compared to conventional instrumentation, PSI significantly reduced total surgical time by 8.9 ± 3.3 min (p=0.038), OR time by 8.6 ± 4.2 min (p=0.043), and the number of instrument trays by six trays (p<0.001). Mechanical axis malalignment of the lower limb of >3° was observed in 13% of PSI patients versus 29% with conventional instrumentation (p=0.043). PSI predicted the size of the femoral and tibial components actually used in 85.9% and 78.9% of cases, respectively.

CONCLUSION

PSI improves alignment, surgical and OR time, reduces the number of instruments trays used compared to conventional instrumentation in patients undergoing TKA and results in fewer outliers in overall mechanical alignment in the coronal plane.

LEVEL OF EVIDENCE II

Prospective comparative therapeutic study.

Clinical alignment variations in total knee arthroplasty with different navigation methods

BACKGROUND

We compared the resulting alignment in 90° of flexion and in full extension after total knee arthroplasty (TKA) with two navigation systems using different techniques: a measured resection (MR) system and a gap - balancing (GB) system.

METHODS

Varus and valgus alignment in extension and flexion was compared in 100 consecutive patients who had TKA with an MR distal-femoral-cut-first technique at one institution and 100 consecutive patients in whom a GB tibial-cut-first technique was used at another institution. Alignment deviation of three degrees or more from neutral was considered an outlier.

RESULTS

No significant difference between the groups in coronal alignment in extension or flexion was found, but there were three times the number of outliers for clinical alignment in flexion for the MR group compared to the GB group.

CONCLUSIONS

The use of the GB tibial-cut-first computer-assisted TKA navigation may provide a more consistent clinical alignment in flexion than systems using an MR technique.

LEVEL OF EVIDENCE

Therapeutic study. Level 2.

Computer-assisted surgery for knee ligament reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) reconstruction is one of the most frequently performed orthopaedic procedures. The most common technical cause of reconstruction failure is graft malpositioning. Computer-assisted surgery (CAS) aims to improve the accuracy of graft placement. Although posterior cruciate ligament (PCL) injury and reconstruction are far less common, PCL reconstruction has comparable difficulties relating to graft placement. This is an update of a Cochrane review first published in 2011.

OBJECTIVES

To assess the effects of computer-assisted reconstruction surgery versus conventional operating techniques for ACL or PCL injuries in adults.

SEARCH METHODS

For this update, we searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (from 2010 to July 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 5, 2013), MEDLINE (from 2010 to July 2013), EMBASE (from 2010 to July 2013), CINAHL (from 2010 to July 2013), article references and prospective trial registers.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-randomized controlled trials that compared CAS for ACL or PCL reconstruction versus conventional operating techniques not involving CAS.

DATA COLLECTION AND ANALYSIS

Two authors independently screened search results, assessed the risk of bias in the studies and extracted data. Where appropriate, we pooled data using risk ratios (RR) or mean differences (MD), both with 95% confidence intervals (CI).

MAIN RESULTS

The updated search resulted in the inclusion of one new study. This review now includes five RCTs with 366 participants. There were more female than male participants (70% were female); their ages ranged from 14 to 53 years. All trials involved ACL reconstructions performed by experienced surgeons.Assessing the studies' risk of bias was hampered by poor reporting of trial methods, and consequently several studies were judged to be 'unclear' for several types of bias. One trial presenting primary outcome data was at high risk of detection bias from lack of clinician blinding and attrition bias from an unaccounted loss to follow-up at two years.We found moderate quality evidence (three trials, 193 participants) of no clinically relevant difference between CAS and conventional surgery in International Knee Documentation Committee (IKDC) subjective scores (self-reported measure of knee function; scale of 0 to 100 where 100 was best function). Pooled data from two of these trials (120 participants) showed a small, but clinically irrelevant difference favouring CAS (MD 2.05, 95% CI -2.16 to 6.25). A third trial (73 participants) also found minimal difference in IKDC subjective scores (reported MD 0.2).We found low quality evidence (two trials, 120 participants) showing no difference between the two groups in Lysholm scores, also measured on a scale 0 to 100 where 100 is best function (MD 0.25, 95% CI -3.75 to 4.25). We found very low quality evidence (one trial, 40 participants) showing no difference between the two groups in Tegner scores. We found low quality evidence (three trials, 173 participants) showing the majority of participants in both groups were assessed as having normal or nearly normal knee function (86/87 with CAS versus 84/86 with no CAS; RR 1.01, 95% CI 0.96 to 1.06).Similarly, no differences were found for our secondary outcome measures of knee stability, loss in range of motion and tunnel placement. None of the trials reported on re-operation.No adverse post-surgical events were reported in two trials (133 participants); this outcome was not reported by the other three trials.CAS use was associated with longer operating times compared with conventional operating techniques: the mean difference in operating times reported in the studies ranged between 9 and 27 minutes.

AUTHORS' CONCLUSIONS

From the available evidence, we are unable to demonstrate or refute a favourable effect of CAS for cruciate ligament reconstructions of the knee compared with conventional reconstructions. However, the currently available evidence does not indicate that CAS in knee ligament reconstruction improves outcome. There is a need for improved reporting of future studies of this technology.

Conventional versus computer-assisted technique for total knee arthroplasty: a minimum of 5-year follow-up of 200 patients in a prospective randomized comparative trial

In the literature, studies of computer-assisted total knee arthroplasty (TKA) after mid-term period are not conclusive and long-term data are rare. In a prospective, randomized, comparative study 100 conventional TKAs (group REG) were compared with 100 computer-assisted TKAs (group NAV). Minimum follow-up was 5years. No difference in implant failure was found with 1.1% in group NAV versus 4.6% in group REG (P=0.368). Group NAV showed a significantly less mean deviation of mechanical limb axis (P=0.015), more TKAs (90% versus 81% in group REG) were within 3° varus/valgus and a higher tibial slope and lateral distal femoral angle (LDFA) accuracy was found (P≤0.034). Clinical investigational parameters showed no differences (P≥0.058). Insall and HSS score total were also higher in group NAV (P≤0.016).

Current data do not support routine use of patient-specific instrumentation in total knee arthroplasty

The purpose of this systematic review and meta-analysis is to compare patient-specific instrumentation (PSI) versus standard instrumentation for total knee arthroplasty (TKA) with regard to coronal and sagittal alignment, operative time, intraoperative blood loss, and cost. A systematic query in search of relevant studies was performed, and the data published in these studies were extracted and aggregated. In regard to coronal alignment, PSI demonstrated improved accuracy in femorotibial angle (FTA) (P=0.0003), while standard instrumentation demonstrated improved accuracy in hip-knee-ankle angle (HKA) (P=0.02). Importantly, there were no differences between treatment groups in the percentages of FTA or HKA outliers (>3 degrees from target alignment) (P=0.7). Sagittal alignment, operative time, intraoperative blood loss, and cost were also similar between groups (P>0.1 for all comparisons).

Computer-assisted surgery for knee ligament reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) reconstruction is one of the most frequently performed orthopaedic procedures. The most common technical cause of reconstruction failure is graft malpositioning. Computer-assisted surgery (CAS) aims to improve the accuracy of graft placement. Although posterior cruciate ligament (PCL) injury and reconstruction are far less common, PCL reconstruction has comparable difficulties relating to graft placement. This is an update of a Cochrane review first published in 2011.

OBJECTIVES

To assess the effects of computer-assisted reconstruction surgery versus conventional operating techniques for ACL or PCL injuries in adults.

SEARCH METHODS

For this update, we searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (from 2010 to July 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 5, 2013), MEDLINE (from 2010 to July 2013), EMBASE (from 2010 to July 2013), CINAHL (from 2010 to July 2013), article references and prospective trial registers.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-randomized controlled trials that compared CAS for ACL or PCL reconstruction versus conventional operating techniques not involving CAS.

DATA COLLECTION AND ANALYSIS

Two authors independently screened search results, assessed the risk of bias in the studies and extracted data. Where appropriate, we pooled data using risk ratios (RR) or mean differences (MD), both with 95% confidence intervals (CI).

MAIN RESULTS

The updated search resulted in the inclusion of one new study. This review now includes five RCTs with 366 participants. There were more female than male participants (70% were female); their ages ranged from 14 to 53 years. All trials involved ACL reconstructions performed by experienced surgeons.Assessing the studies' risk of bias was hampered by poor reporting of trial methods, and consequently several studies were judged to be 'unclear' for several types of bias. One trial presenting primary outcome data was at high risk of detection bias from lack of clinician blinding and attrition bias from an unaccounted loss to follow-up at two years.We found moderate quality evidence (three trials, 193 participants) of no clinically relevant difference between CAS and conventional surgery in International Knee Documentation Committee (IKDC) subjective scores (self-reported measure of knee function; scale of 0 to 100 where 100 was best function). Pooled data from two of these trials (120 participants) showed a small, but clinically irrelevant difference favouring CAS (MD 2.05, 95% CI -2.16 to 6.25). A third trial (73 participants) also found minimal difference in IKDC subjective scores (reported MD 0.2).We found low quality evidence (two trials, 120 participants) showing no difference between the two groups in Lysholm scores, also measured on a scale 0 to 100 where 100 is best function (MD 0.25, 95% CI -3.75 to 4.25). We found very low quality evidence (one trial, 40 participants) showing no difference between the two groups in Tegner scores. We found low quality evidence (three trials, 173 participants) showing the majority of participants in both groups were assessed as having normal or nearly normal knee function (86/87 with CAS versus 84/86 with no CAS; RR 1.01, 95% CI 0.96 to 1.06).Similarly, no differences were found for our secondary outcome measures of knee stability, loss in range of motion and tunnel placement. None of the trials reported on re-operation.No adverse post-surgical events were reported in two trials (133 participants); this outcome was not reported by the other three trials.CAS use was associated with longer operating times compared with conventional operating techniques: the mean difference in operating times reported in the studies ranged between 9 and 27 minutes.

AUTHORS' CONCLUSIONS

From the available evidence, we are unable to demonstrate or refute a favourable effect of CAS for cruciate ligament reconstructions of the knee compared with conventional reconstructions. However, the currently available evidence does not indicate that CAS in knee ligament reconstruction improves outcome. There is a need for improved reporting of future studies of this technology.

Less outliers in pinless navigation compared with conventional surgery in total knee arthroplasty

PURPOSE

The aim of this study was to investigate the effectiveness of a new pinless navigation system (BrainLAB(®) VectorVision(®) Knee 2.5 Navigation System) as an intra-operative alignment check in total knee arthroplasty using conventional cutting jigs.

METHODS

200 patients who underwent total knee arthroplasty using conventional technique or pinless navigation by a senior surgeon were included in the study and prospectively followed up. Intra-operative readings from the pinless navigation system were recorded, and post-operative long limb radiographic films were taken. The accepted values for normal alignment were 180 ± 3° for Hip-Knee-Ankle Angle and 90 ± 3° for Coronal Femoral-Component Angle or Coronal Tibia-Component Angle.

RESULTS

There was no difference in the duration of surgery. The mean Coronal Femoral-Component Angle was 89.8 ± 2.0° and 91.3 ± 2.3° in the pinless navigation and conventional group, respectively (p < 0.001). For Hip-Knee-Ankle Angle, the proportion of outliers was 10 % in the pinless navigation group compared to 26 % in the conventional group (p = 0.005). For Coronal Femoral-Component Angle and Coronal Tibia-Component Angle, the proportion of outliers was 7 and 4 %, respectively, in the pinless navigation group, compared to 22 and 19 % in the conventional group (p = 0.004 and p = 0.001, respectively). The measurements of Coronal Femoral-Component Angle and Coronal Tibia-Component Angle on post-operative radiographic films were similar to intra-operative readings.

CONCLUSIONS

This study showed that pinless navigation is an effective tool for reducing the proportion of outliers, without significantly increasing the duration of surgery. The authors recommend its use in total knee arthroplasty using conventional cutting jigs.

No effect of obesity on limb and component alignment after computer-assisted total knee arthroplasty

PURPOSE

This retrospective study aimed to determine if computer navigation provides consistent accuracy for limb and component alignment during TKA irrespective of body mass index (BMI) by comparing limb and component alignment and the outlier rates in obese versus non-obese individuals undergoing computer-assisted TKA.

METHODS

Six hundred and thirty-five computer assisted total knee arthroplasties (TKAs) performed in non-obese individuals (BMI<30 kg/m(2)) were compared with 520 computer-assisted TKAs in obese individuals (BMI ≥ 30 kg/m(2)) for postoperative limb and component alignment using full length standing hip-to-ankle radiographs.

RESULTS

No significant difference in postoperative limb alignment (179.7° ± 1.7° vs 179.6° ± 1.8°), coronal femoral (90.2° ± 1.6° vs 89.8° ± 1.9°) and tibial component (90.2° ± 1.6° vs 90.3° ± 1.7°) alignment and outlier rates (6.2% vs 7.5%) was found between non-obese and obese individuals. Similarly, alignment and the outlier rates were similar when non-obese individuals and a subgroup of morbidly obese individuals (BMI >40 kg/m(2)) were compared.

CONCLUSIONS

Computer navigation can achieve excellent limb and component alignment irrespective of a patient's BMI. Although obesity may not be an indication per se for using computer navigation during TKA, it will help achieve consistently accurate limb and component alignment in obese patients.

LEVEL OF EVIDENCE

Level II.

No difference in accuracy between pinless and conventional computer-assisted surgery in total knee arthroplasty

PURPOSE

Many studies have demonstrated higher precision and better radiological results in Total knee arthroplasty (TKA) with computer-assisted surgery (CAS). On the other hand, studies revealed a lengthening of operation time up to 20 min for this technique and demonstrated rare additional complications as fractures and neurovascular injuries caused by the array pins and any intraoperative array dislocation leads to abortion of CAS. To combine the advantages and eliminate the disadvantages of standard CAS, we evaluated the accuracy of a so-called pinless CT-free version of knee navigation (pinless CAS) abandoning the reference pins and reducing the necessary workflow to a minimum.

METHOD

The present study compares the accuracy of the reference methods of two different CT-free knee navigation software versions (Brainlab Knee 2.1 and Brainlab Knee Express 2.5). Thirty patients received TKA assisted by standard CAS. Intraoperatively, the proposed bony resections of standard CAS were matched with the new pinless CAS. Postoperatively, the results were checked by evaluating the radiographs concerning leg axis, femoral flexion and tibial slope.

RESULTS

All results concerning precise cuts (femoral as well as tibial coronal/varus-valgus alignment, femoral flexion alignment and tibial slope, resection height) were comparable between both groups (n.s.). In femoral, we found a mean deviation of coronal alignment of 0.3° (SD 0.7) and flexion of 0.2° (SD 0.8). In tibial, we found a mean deviation of coronal alignment of 0.2° (SD 0.5) and slope of 0.2° (SD 0.6). The mean additional operation time for the pinless CAS was below 2 min. The postoperative mechanical leg axis was within the threshold of 3° in all patients, tibial slope and femoral flexion matched with CAS values.

CONCLUSION

In clinical routine, pinless CAS can comprise the advantages of CAS leaving the disadvantages aside. It reduces surgical time and avoids complications associated with the tracking pins of conventional CAS.

Repeatability and accuracy of a non-invasive method of measuring internal and external rotation of the tibia

PURPOSE

The ability to quantify rotational laxity of the knee would increase understanding of functional rotatory instability, identify the best treatment methods for soft tissue injury, and have a role in diagnosis of soft tissue injury. This study aimed to report the reliability, repeatability and precision of a non-invasive adaptation of image-free navigation technology by comparing with a validated invasive system used for computer-assisted surgery.

METHODS

Twelve cadaveric lower limbs were tested with a commercial image-free navigation system using passive trackers secured by bone screws. They were then tested a non-invasive fabric-strap system. Manual application of torque was used consistent with clinical examination to rotate the tibia to the end of internal rotation and external rotation range. Measurements were taken at 10° intervals from full extension to 90° flexion, and protocol was repeated twice using each system. Intraclass correlation coefficient (ICC) was used to reflect reliability of measurements. At each flexion interval, coefficient of repeatability (CR) was calculated for each system, and limits of agreement (LOA) were used to reflect agreement between the systems.

RESULTS

The results for internal and external rotation were combined throughout flexion: ICC invasive; 0.94 (0.86-0.99), non-invasive; 0.92 (0.7-0.99), CR invasive; 2.4° (1.3-4.8°), non-invasive; 3.5° (1.8-6.6), LOA; 8.2° (4.3-13.5).

CONCLUSION

Non-invasive optical tracker fixation gives improved agreement with a validated method of measurement compared with devices measuring tibial rotation by foot position. This system gives the added possibility of dynamic, weight-bearing testing in the clinically important range of 0°-30° knee flexion without the need for any limb restraint.

Coronal alignment in total knee replacement

Substantial healthcare resources have been devoted to computer navigation and patient-specific instrumentation systems that improve the reproducibility with which neutral mechanical alignment can be achieved following total knee replacement (TKR). This choice of alignment is based on the long-held tenet that the alignment of the limb post-operatively should be within 3° of a neutral mechanical axis. Several recent studies have demonstrated no significant difference in survivorship when comparing well aligned versus malaligned TKRs. Our aim was to review the anatomical alignment of the knee, the historical and contemporary data on a neutral mechanical axis in TKR, and the feasibility of kinematically-aligned TKRs.

Review of the literature suggests that a neutral mechanical axis remains the optimal guide to alignment.

Cite this article: Bone Joint J 2014;96-B:857–62.

Evaluation of a CT-based technique to measure the transfer accuracy of a virtually planned osteotomy

Accurate transfer of a preoperatively planned osteotomy plane to the bone is of significance for corrective surgery, tumor resection, implant positioning and evaluation of new osteotomy techniques. Methods for comparing a preoperatively planned osteotomy plane with a surgical cut exist but the accuracy of these techniques are either limited or unknown. This paper proposes and evaluates a CT-based technique that enables comparing virtual with actual osteotomy planes. The methodological accuracy and reproducibility of the technique is evaluated using CT-derived volume data of a cadaver limb, which serves to plan TKA osteotomies in 3-D space and to simulate perfect osteotomies not hampered by surgical errors. The methodological variability of the technique is further investigated with repeated CT scans after actual osteotomy surgery of the same cadaver specimen. Plane displacement (derr) and angulation errors in the sagittal and coronal plane (βerr, γerr) are measured with high accuracy and reproducibility (derr=-0.11±0.06mm; βerr=0.08±0.04°, γerr=-0.03±0.03°). The proposed method for evaluating an osteotomy plane position and orientation has a high intrinsic accuracy and reproducibility. The method can be of great value for measuring the transfer accuracy of new techniques for positioning and orienting a surgical cut in 3-D space.

A comparison of variable angle versus fixed angle distal femoral resection in primary total knee arthroplasty

This study assessed whether using a variable distal valgus resection angle improved post-operative coronal lower limb alignment in total knee arthroplasty (TKA). Two groups were compared: Fixed (n = 124), where a fixed distal valgus resection angle of 7° was used; Variable (n = 87), where the resection angle was adjusted to the measured femoral mechanical anatomical (FMA) angle of the patient. FMA and mechanical femoro-tibial (MFT) angles were measured on pre-operative and post-operative hip-knee-ankle radiographs. 85% of patients in the Variable group had a post-operative MFT angle within 0° ± 3°compared to 69% in the Fixed group (P = 0.006). The use of a fixed distal femoral resection angle for all patients is not appropriate. Setting the resection to an individual patient's FMA angle can significantly improve the post-operative MFT angle.

Influence of the optical system and anatomic points on computer-assisted total knee arthroplasty

BACKGROUND

For over a decade, computer-assisted orthopaedic surgery for total knee arthroplasty has been accepted as ensuring accurate implant alignment in the coronal plane.

HYPOTHESIS

We hypothesised that lack of accuracy in skeletal landmark identification during the acquisition phase and/or measurement variability of the infrared optical system may limit the validity of the numerical information used to guide the surgical procedure.

METHODS

We built a geometric model of a navigation system, with no preoperative image acquisition, to simulate the stages of the acquisition process. Random positions of each optical reflector center and anatomic acquisition point were generated within a sphere of predefined diameter. Based on the virtual geometric model and navigation process, we obtained 30,000 simulations using the Monte Carlo statistical method then computed the variability of the anatomic reference frames used to guide the bone cuts. Rotational variability (α, β, γ) of the femoral and tibial landmarks reflected implant positioning errors in flexion-extension, valgus-varus, and rotation, respectively.

RESULTS

Taking into account the uncertainties pertaining to the 3D infrared optical measurement system and to anatomic point acquisition, the femoral and tibial landmarks exhibited maximal alpha (flexion-extension), beta (valgus-varus), and gamma (axial rotation) errors of 1.65° (0.9°); 1.51° (0,98°), and 2.37° (3.84°), respectively. Variability of the infrared optical measurement system had no significant influence on femoro-tibial alignment angles.

CONCLUSION

The results of a Monte Carlo simulation indicate a certain level of vulnerability of navigation systems for guiding position in rotation, contrasting with robustness for guiding sagittal and coronal alignments.

LEVEL OF EVIDENCE

Level IV.

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.

Functional outcome and alignment in computer-assisted and conventionally operated total knee replacements

We performed a randomised controlled trial comparing computer-assisted surgery (CAS) with conventional surgery (CONV) in total knee replacement (TKR). Between 2009 and 2011 a total of 192 patients with a mean age of 68 years (55 to 85) with osteoarthritis or arthritic disease of the knee were recruited from four Norwegian hospitals. At three months follow-up, functional results were marginally better for the CAS group. Mean differences (MD) in favour of CAS were found for the Knee Society function score (MD: 5.9, 95% confidence interval (CI) 0.3 to 11.4, p = 0.039), the Knee Injury and Osteoarthritis Outcome Score (KOOS) subscales for ‘pain’ (MD: 7.7, 95% CI 1.7 to 13.6, p = 0.012), ‘sports’ (MD: 13.5, 95% CI 5.6 to 21.4, p = 0.001) and ‘quality of life’ (MD: 7.2, 95% CI 0.1 to 14.3, p = 0.046). At one-year follow-up, differences favouring CAS were found for KOOS ‘sports’ (MD: 11.0, 95% CI 3.0 to 19.0, p = 0.007) and KOOS ‘symptoms’ (MD: 6.7, 95% CI 0.5 to 13.0, p = 0.035). The use of CAS resulted in fewer outliers in frontal alignment (> 3° malalignment), both for the entire TKR (37.9% vs 17.9%, p = 0.042) and for the tibial component separately (28.4% vs 6.3%, p = 0.002). Tibial slope was better achieved with CAS (58.9% vs 26.3%, p < 0.001). Operation time was 20 minutes longer with CAS. In conclusion, functional results were, statistically, marginally in favour of CAS. Also, CAS was more predictable than CONV for mechanical alignment and positioning of the prosthesis. However, the long-term outcomes must be further investigated.

Cite this article: Bone Joint J 2014; 96-B:609–18.

[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.

Collateral soft tissue release in primary total knee replacement

The aim of this study was to assess the rate of collateral soft tissue release required in navigated total knee arthroplasty (TKA) to achieve an intra-operative coronal femoral tibial mechanical axis (FTMA) in extension of 0 ± 2°. The primary outcomes assessed were post-operative coronal plane alignment and rate of collateral soft tissue release. The secondary outcomes were range of motion, function, patient satisfaction, and complication rates at one-year follow-up. This is a prospective study of 224 knees. No exclusions were made on the basis of pathology or severity of deformity. Pre-operative FTMA ranged from 27° valgus to 25° varus (mean: -4.5° SD 7.6). Soft tissue release was carried out in 5 of 224 knees (2.2%). Post-operative weight-bearing radiological FTMA ranged from 7° valgus to 8° varus (mean: -0.4° SD 2.5°). Two hundred and ten knees (96%) were within 0 ± 5° of neutral. At one year, median maximum flexion was 100° (IQR 15°) and extension was 0°; mean post-operative Oxford Knee Score had improved from 42 to 23; and 91% of patients were satisfied or very satisfied, with only 2% being dissatisfied. We have found that in the vast majority of cases, including those with large pre-operative coronal deformity in extension, good outcomes in terms of coronal alignment, range of movement, function and patient satisfaction can be achieved.

Defining the errors in the registration process during imageless computer navigation in total knee arthroplasty: a cadaveric study

Computer assisted arthroplasty was introduced as a means to optimally align implants in order to improve function and longevity. The error during the manual registration of landmarks and its effect on component alignment was investigated in this study. Five fresh frozen lower limbs were used and the registration process was performed five times by five surgeons. The error range of the mechanical axis of the femur in the coronal plane was 5.2 degrees of valgus to 2.9 degrees of varus whilst the transepicondylar axis error was 11.1 degrees of external to 6.3 of internal rotation. Those figures suggest that the registration error alone can have a significant effect on the alignment of the implant.

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.

Patient-specific instrumentation improves tibial component rotation in TKA

PURPOSE

To compare the femoral and tibial components rotational alignment in total knee arthroplasty (TKA) performed either with conventional or with patient-specific instrumentation.

METHODS

Forty-five patients underwent primary TKA and were prospectively randomized into two groups: 22 patients into the conventional instrumentation group (group A) and 23 patients into the Signature™ patient-specific instrumentation group (group B). All patients underwent computed tomography of the operated knee in the first week after surgery to measure the components rotation.

RESULTS

The femoral component rotation was 0.0° (-0.25, 1.0) in group A, and 0.0° (0.0, 1.0) in group B. The tibial component rotation was -16.0° (-18.5, 11.8) in group A, and -16.0° (-19.0, -14.0) in group B. There were no significant differences between the two groups in tibial and femoral components rotation. The difference between the tibial component rotation and the neutral tibial rotation was similar in both groups [2.0° (-0.5, 6.3) in group A and 2.0° (-1.0, 4.0) in group B], but the dispersion around the median was different between the two groups. The amplitude of the difference between tibial rotation and neutral position was 27° (-13, 14) in group A and 9° (-3, 6) in group B.

CONCLUSIONS

There is a smaller chance of internal malrotation of the tibial component with the Signature™ patient-specific instrumentation system, with less dispersion and amplitude of the tibial component rotation around the neutral position.

LEVEL OF EVIDENCE

II.

The radiological outcomes of patient-specific instrumentation versus conventional total knee arthroplasty

PURPOSE

The aim of this study was to investigate the post-operative radiological outcomes of patient-specific instrumentation (PSI) surgery versus conventional total knee arthroplasty (TKA).

METHODS

Sixty patients scheduled for a primary TKA were prospectively divided into PSI or conventional technique. Coronal and sagittal radiographic long limb films were taken post-operatively. The accepted values for normal alignment were 180° ± 3° for hip-knee-ankle angle; 90° ± 3° for coronal femoral component angle or coronal tibia component angle; 0° to 3° flexion for sagittal femoral component angle and 0° to 7° posterior slope for sagittal tibia component angle.

RESULTS

For hip-knee-ankle angle, there were 21 % more outliers in the PSI group compared to the conventional group (p = 0.045). Most of these outliers had valgus deformity in the PSI group and varus deformity in the conventional group (p = 0.045). For implant placement, there was no difference in the proportion of outliers between the two groups. There was also no difference in the duration of surgery.

CONCLUSIONS

This study showed that PSI surgery is associated with a larger proportion of outliers for lower limb alignment. PSI surgery as an alternative to conventional TKA is not advisable.

LEVEL OF EVIDENCE

II.

Current concepts in knee replacement: features and imaging assessment

OBJECTIVE

This article reviews current concepts of knee replacement. Features of traditional and new prosthetic designs, materials, and surgical techniques are discussed. Normal and abnormal postoperative imaging findings are illustrated. Complications are reviewed and related to the current understanding about how and why these failures occur.

CONCLUSION

It is well known that after knee replacement, patients with complications may be asymptomatic, and, for this reason, assessment of postoperative imaging is important. The foundation of radiologic interpretation of knee replacement is knowledge of the physiologic purpose, orthopedic trends, imaging findings, and complications.

The accuracy of component alignment in custom cutting blocks compared with conventional total knee arthroplasty instrumentation: prospective control trial

BACKGROUND

The purpose of this study was to assess whether custom cutting blocks improve accuracy of component alignment compared to conventional TKA instrumentation.

METHODS

Eighty primary TKA patients were enrolled in an open-label randomized prospective clinical trial and were divided into two groups, 40 custom cutting blocks and 40 conventional TKA instrumentations. The primary outcome was prosthetic alignment with respect to mechanical axis and epicondylar axis. Secondary outcomes included operative time, 24-hour postoperative blood loss and hemoglobin at discharged.

RESULTS

There were no statistical significant differences in the postoperative mechanical axis between the custom cutting blocks group and conventional TKA group, (95% vs. 87.5% within 3° of neutral mechanical alignment, p=0.192). The average rotational alignment was statistically significantly different in the custom cutting blocks group (1.0°±0.6° vs. 1.6°±1.8° external rotation from epicondylar axis, p<0.001). There were statistical significant differences in operation time between custom cutting blocks group and conventional group, skin to skin [57.5±2.3 min vs. 62.1±1.5, p<0.001]. We found an improvement in group 1 compared with group 2 regarding the proportion of patients with postoperative blood loss within 24 h.

CONCLUSIONS

Custom cutting blocks technique was a surgical procedure which provided better accuracy in rotational alignment but no statistical differences in mechanical axis, less operative time and reduced blood loss than the conventional TKA instrumentation in the majority of patients.

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%).

Intraoperative fluoroscopy improves surgical precision in conventional TKA

PURPOSE

The purpose of this study was to assess whether intraoperative fluoroscopy assists in the restoration of the coronal limb alignment target in conventional total knee arthroplasty (TKA).

METHODS

One hundred and six patients undergoing conventional cemented TKA were randomly assigned to be operated on with or without intraoperative fluoroscopy. The image intensifier, together with customized manual instrumentation, was used for separately measuring the frontal alignment of the femoral and tibial resection surfaces. The surgeon adjusted the resection surfaces when a mechanical axis deviation error angle of ≥ 0.5° was observed on the fluoroscopic image. Coronal alignment was measured on standing long-leg digital radiographs.

RESULTS

Patients operated with fluoroscopy assistance had (1) a lower risk of malalignment at the threshold of >3° (risk ratio, 0.7; 95 % CI, 0.13-1.2), (2) a mean fluoroscopic time of 3 s, and (3) a longer operative time (69 vs. 60 min, p < 0.001). The American Knee Society Score was not different between the two groups at 1-year follow-up.

CONCLUSION

This new surgical intervention appears to offer an effective means for improving the precision of TKA alignment in the coronal plane.

Patient-specific guides do not improve accuracy in total knee arthroplasty: a prospective randomized controlled trial

BACKGROUND

Recently, patient-specific guides (PSGs) have been introduced, claiming a significant improvement in accuracy and reproducibility of component positioning in TKA. Despite intensive marketing by the manufacturers, this claim has not yet been confirmed in a controlled prospective trial.

QUESTIONS/PURPOSES

We (1) compared three-planar component alignment and overall coronal mechanical alignment between PSG and conventional instrumentation and (2) logged the need for applying changes in the suggested position of the PSG.

METHODS

In this randomized controlled trial, we enrolled 128 patients. In the PSG cohort, surgical navigation was used as an intraoperative control. When the suggested cut deviated more than 3° from target, the use of PSG was abandoned and marked as an outlier. When cranial-caudal position or size was adapted, the PSG was marked as modified. All patients underwent long-leg standing radiography and CT scan. Deviation of more than 3° from the target in any plane was defined as an outlier.

RESULTS

The PSG and conventional cohorts showed similar numbers of outliers in overall coronal alignment (25% versus 28%; p = 0.69), femoral coronal alignment (7% versus 14%) (p = 0.24), and femoral axial alignment (23% versus 17%; p = 0.50). There were more outliers in tibial coronal (15% versus 3%; p = 0.03) and sagittal 21% versus 3%; p = 0.002) alignment in the PSG group than in the conventional group. PSGs were abandoned in 14 patients (22%) and modified in 18 (28%).

CONCLUSIONS

PSGs do not improve accuracy in TKA and, in our experience, were somewhat impractical in that the procedure needed to be either modified or abandoned with some frequency.

No difference in ROM and knee function between mobile and floating platforms in TKA

PURPOSE

The purpose of this study was to determine whether the floating platforms (FP) were superior to rotating platforms (RP) in computer-navigated total knee arthroplasty (TKA) comparing the range of motion (ROM) as well as clinical and subjective function of the knee.

METHODS

This retrospective non-randomized single-centre cohort study includes 255 patients with a primary implanted computer-navigated e.motion™ (Aesculap B. Braun) TKA system, implanted because of clinical and radiological verified gonarthrosis. In 129 patients, the FP platform was implanted, and in 126 patients, the RP platform. As statistical procedures for differences between inlay type RP/FP in ROM and Knee Society Score (KSS) after 3- and 24-month follow-up, an analysis of covariance (with risk factors gender, age, BMI, preoperative ROM and preoperative KSS) was performed.

RESULTS

Although preoperative ROM and knee society function score (KSS part II) were significantly higher in the FP group before surgery, there was no significant difference between RP and FP in ROM and KSS at 3- and 24-month follow-up.

CONCLUSION

The FP platform design did not have an advantage in ROM as well as in clinical and subjective knee function compared with the RP platform in computer-navigated TKA neither in early follow-up examinations at 3 months postoperatively nor at long-time follow-up at 24 months postoperatively.

Is TKA using patient-specific instruments comparable to conventional TKA? A randomized controlled study of one system

BACKGROUND

Patient-specific CT-based instrumentation may reduce implant malpositioning and improve alignment in TKA. However, it is not known whether this innovation is an advance that benefits patients.

QUESTIONS/PURPOSES

We evaluated (1) the precision of patient-specific TKA by comparing the incidence of outliers in postoperative alignment between TKAs using patient-specific instruments and TKAs using conventional instruments, and (2) the reliability of patient-specific instruments by intraoperatively investigating whether the surgery could be completed with patient-specific instruments alone.

METHODS

In this randomized controlled trial, we compared patient-specific TKA instruments from one manufacturer (n = 50) with conventional TKA instruments (n = 50). Postoperative hip-knee-ankle angles, femoral component rotation, and coronal and sagittal alignments of each component were measured. The validity of the patient-specific instrument was examined using cross-checking procedures with conventional instruments during the surgeries. When the procedure could not be completed accurately with patient-specific instruments, the procedure was converted to TKA using conventional instruments, and the frequency of this occurrence was tallied.

RESULTS

Outliers in the hip-knee-ankle angle were comparable between groups (12% in the patient-specific instrument group and 10% in the conventional instrument group). Other parameters such as sagittal alignment and femoral component rotation did not differ in terms of outliers. Patient-specific guides were abandoned in eight knees (16%) during the surgery because of malrotation of the femoral components and decreased slope of the tibia.

CONCLUSIONS

Accuracy was comparable between TKAs done with patient-specific instruments and those done with conventional instruments. However, the patient-specific instrument procedures had to be aborted frequently, incurring expenses that did not benefit patients.

Improved accuracy in computer-assisted unicondylar knee arthroplasty: a meta-analysis

PURPOSE

Inaccurate implantation rates of up to 30 % have been reported in cases using the conventional technique for implantation of a unicompartmental knee arthroplasty. Navigation should permit a more precise implantation, and several studies have investigated its role, albeit with a limited number of patients and inconsistent results. The aim of this meta-analysis was to compare risks of unsatisfactory outcomes in patients with navigated and conventional technique.

METHODS

An electronic search was performed, and ten studies were eligible and included in the meta-analysis, with a total of 258 prostheses implanted with the navigated technique and 295 with the conventional one. The following items were analysed: radiological positioning of the femoral and the tibial component in the AP and lateral view, radiological analysis of the tibiofemoral mechanical axis and the difference in operating time between the two groups. Relative risks (RR) were calculated from the reported percentages of implants outside the optimal ranges defined by the manufacturers or the study groups. Natural logarithms of the relative risks were pooled by means of random effects models.

RESULTS

For all the analysed radiological parameters, the RR of measurements outside the optimal ranges were less than 1 in the navigation group suggesting a reduction in the risk of outliers with navigation. The average operating time in the navigated group was 15.4 min (95 % CI: 10.2-20.6) longer than in the conventional group.

CONCLUSION

The meta-analysis shows that the use of navigation systems in UKA leads to a more precise component position. Whether the more accurate position in UKA results in a better clinical outcome or long-term survival is yet unknown. Nevertheless, as a precise implant position appears to be beneficial, the use of navigation should be recommended for UKA. The limits defined by the manufacturers for an optimal positioning are not consistent.

A new navigation-based technique for lateral distalizing condylar osteotomy in patients undergoing total knee arthroplasty with fixed valgus deformity

PURPOSE

In a prospective, consecutive study, a navigation-based technique for calculating the sliding distance of the lateral epicondyle prior to osteotomy in TKA surgery of fixed valgus deformity has been developed, and early results have been evaluated.

MATERIALS AND METHODS

Twenty-seven knees with a fixed valgus deformity undergoing TKA received this new treatment. Clinical scores and radiograph evaluation were performed preoperatively and 1-year postoperatively. Static and dynamic kinematic data were obtained from navigation at the beginning and at the end of surgery.

RESULTS

The calculated amount of sliding distance varied between 5 and 16 mm. No complications regarding this technique occurred. All clinical scores showed a significant improvement, and radiological evaluation showed a correction of all parameters in 100 % of patients.

CONCLUSION

With this navigation-based technique, it is possible to calculate the amount of sliding distance prior to osteotomy and obtain excellent early results. All axes have been corrected completely, and flexion and extension gaps were balanced. No specific complications of this technique have occurred so far.

LEVEL OF EVIDENCE

II.

Three-dimensional motion analysis of the human knee joint: comparison between intra- and post-operative measurements

PURPOSE

To compare intra-operative knee joint kinematic measurements immediately after total knee replacement with those of the same patients post-operatively at 6-month follow-up.

METHODS

Fifteen patients who underwent total knee arthroplasty were analysed retrospectively. Eight were implanted with one prosthesis design and seven with another. The intra-operative measurements were performed by using a standard knee navigation system. This provided accurate three-dimensional positions and orientations for the femur and tibia by corresponding trackers pinned into the bones. At 6-month follow-up, the patients were analysed by standard three-dimensional video-fluoroscopy of the replaced knee during stair climbing, chair rising and step-up. Relevant three-dimensional positions and orientations were obtained by an iterative shape-matching procedure between the silhouette contours and the CAD-model projections. A number of traditional kinematic parameters were calculated from both measurements to represent the joint motion.

RESULTS

Good post-operative replication of the intra-operative measurements was observed for most of the variables analysed. The statistical analysis also supported the good consistency between the intra- and post-operative measurements.

CONCLUSIONS

Intra-operative kinematic measurements, accessible by a surgical navigation system, are predictive of the following motion performance of the replaced knees as experienced in typical activities of daily living.

LEVEL OF EVIDENCE

Prognostic studies--investigating natural history and evaluating the effect of a patient characteristic, Level II.

Can technology improve alignment during knee arthroplasty

Component malalignment remains a concern in total knee arthroplasty (TKA); therefore, a series of technologies have been developed to improve alignment. The authors conducted a systematic review to compare computer-assisted navigation with conventional instrumentation, and assess the current evidence for patient-matched instrumentation and robot-assisted implantation. An extensive search of the PubMed database for relevant meta-analyses, systematic reviews and original articles was performed, with each study scrutinised by two reviewers. Data on study characteristics and outcomes were extracted from each study and compared. In total 30 studies were included: 10 meta-analyses comparing computer-assisted navigation and conventional instrumentation, 13 studies examining patient-matched instrumentation, and seven investigating robot-assisted implantation. Computer-assisted navigation showed significant and reproducible improvements in mechanical alignment over conventional instrumentation. Patient-matched instrumentation appeared to achieve a high degree of mechanical alignment, although the majority of studies were of poor quality. The data for robot-assisted surgery was less indicative. Computer-assisted navigation improves alignment during TKA over conventional instrumentation. For patient-matched instrumentation and robot-assisted implantation, alignment benefits have not been reliably demonstrated. For all three technologies, clinical benefits cannot currently be assumed, and further studies are required. Although current technologies to improve alignment during TKA appear to result in intra-operative benefits, their clinical impact remains unclear, and surgeons should take this into account when considering their adoption.

The role of navigation in total knee replacement surgery

Since the introduction of modern implants in the 1970s, total knee replacement surgery has been a great clinical and commercial success. Implants and techniques have continued to evolve, driven by the desire for improved function and longevity. However, inaccurate insertion of these implants may cause them to loosen and fail. Computer navigation has been introduced as a modification to existing surgical techniques to improve the accuracy with which the bones are cut prior to inserting the knee replacement implants. Research continues to see if this potentially costly and time consuming technique can contribute to improved longevity of knee replacements.

Computer navigation is a useful intra-operative tool for joint line measurement in total knee arthroplasty

BACKGROUND

Restoration of the native joint line in total knee arthroplasty is important in restoring ligamentous balance and normal knee kinematics. Failure to achieve this could lead suboptimal outcomes. The purpose of this study was to analyze the clinical and functional outcome of patients who demonstrated joint line changes after computer-assisted (CAS) total knee arthroplasty (TKA).

METHODS

One hundred sixty-eight patients (168 knees) underwent CAS TKA by two surgeons at a single institution with 2 years follow-up. The final change in joint line was calculated from the verified tibial resection and distal femoral cuts. Group A patients had joint line changes of less than 4mm and Group B patients had joint line changes of more than 4mm. Post-operative Oxford scores, Knee scores, Function scores and SF-36 scores were obtained at 6 months and 2 years post TKA.

RESULTS

There was significant linear correlation between joint line changes and Oxford scores (P=0.0001), Function scores (P=0.0001) and Knee scores (P=0.0001) at 6 months and Oxford scores (P=0.0001) alone at 2 years with increasing joint line changes having poorer outcome scores. Group A compared to Group B patients demonstrated better Oxford scores (P=0.0001), Function scores (P=0.0001), Knee scores (P=0.0001) and total SF-36 scores (P=0.003) at 6 months as well as better Oxford scores (P=0.0001) and Knee scores (P=0.014) at 2 years.

CONCLUSIONS

CAS is a useful intra-operative tool for assessing the final joint line in TKA. Outliers in joint line changes of ≥4 mm are associated with poorer clinical outcome scores.

LEVEL OF EVIDENCE

Prognostic Study, Level II-1.

Training benefits of computer navigated total knee arthroplasty

BACKGROUND

Computer navigation aims to improve the surgical accuracy of total knee replacement by more reliably placing the cutting blocks in the optimum location in order to create a neutral mechanical axis. Aside from the obvious clinical benefit to the patient, we believe computer navigation has a valuable role as a training tool. The aim of this study is to demonstrate the effectiveness of computer navigation as a training tool in total knee arthroplasty.

METHODS

We performed a training exercise using Sawbone plastic models to simulate four common sources of error in the saw technique; 1. cutting guide movement due to inadequate fixation, 2. the effect of using slotted or open cutting guides, 3. the effect of bending the saw blade, and 4. the effect of recutting on the accuracy of the intended resection.

RESULTS

We found that bony resection errors resulted from; use of less than three pins to fix the cutting guide, use of open cutting guides, deliberate and inadvertent "hanging" or "lifting" of the saw on the cutting guide and recutting after moving the cutting guide.

CONCLUSION

The immediate feedback provided by computer navigated TKA allows surgeons and trainee surgeons the opportunity to improve the accuracy of their technique and increase awareness of their individual sources of error in TKA.

CLINICAL RELEVANCE

Used as a teaching tool, computer navigation can immediately identify errors in surgical technique and target subsequent training to minimise these errors. Training can be conducted whilst ensuring there is no detriment to patient safety.

An economic model to evaluate cost-effectiveness of computer assisted knee replacement surgery in Norway

BACKGROUND

The use of Computer Assisted Surgery (CAS) for knee replacements is intended to improve the alignment of knee prostheses in order to reduce the number of revision operations. Is the cost effectiveness of computer assisted surgery influenced by patient volume and age?

METHODS

By employing a Markov model, we analysed the cost effectiveness of computer assisted surgery versus conventional arthroplasty with respect to implant survival and operation volume in two theoretical Norwegian age cohorts. We obtained mortality and hospital cost data over a 20-year period from Norwegian registers. We presumed that the cost of an intervention would need to be below NOK 500,000 per QALY (Quality Adjusted Life Year) gained, to be considered cost effective.

RESULTS

The added cost of computer assisted surgery, provided this has no impact on implant survival, is NOK 1037 and NOK 1414 respectively for 60 and 75-year-olds per quality-adjusted life year at a volume of 25 prostheses per year, and NOK 128 and NOK 175 respectively at a volume of 250 prostheses per year. Sensitivity analyses showed that the 10-year implant survival in cohort 1 needs to rise from 89.8% to 90.6% at 25 prostheses per year, and from 89.8 to 89.9% at 250 prostheses per year for computer assisted surgery to be considered cost effective. In cohort 2, the required improvement is a rise from 95.1% to 95.4% at 25 prostheses per year, and from 95.10% to 95.14% at 250 prostheses per year.

CONCLUSIONS

The cost of using computer navigation for total knee replacements may be acceptable for 60-year-old as well as 75-year-old patients if the technique increases the implant survival rate just marginally, and the department has a high operation volume. A low volume department might not achieve cost-effectiveness unless computer navigation has a more significant impact on implant survival, thus may defer the investments until such data are available.

Applications of computer navigation in sports medicine knee surgery: an evidence-based review

Computer-assisted surgery (CAS) has been investigated in a number of sports medicine procedures in the knee. Current barriers to its widespread introduction include increased costs, duration, and invasiveness of surgery. Randomized trials on the use of CAS in anterior cruciate ligament reconstruction have failed to demonstrate a clinical benefit. Data on CAS use in high tibial osteotomy are more promising; however, long-term studies are lacking. CAS has a number of research applications in knee ligament surgery, and studies continue to explore its use in the treatment of osteochondral lesions. This article reviews the applications of CAS in sports medicine knee surgery and summarizes current literature on clinical outcomes.

Influence of navigation system updates on total knee arthroplasty

BACKGROUND

The purpose of this study was to evaluate the influence of image-free computer-assisted navigation system update on outcome in total knee arthroplasty.

METHODS

Thirty-three knees were replaced using the Stryker 3.1 image-free navigation system and 49 knees were replaced using the Stryker 4.0 system. One surgeon took part in all procedures as chief surgeon or first assistant. All patients received the Stryker Scopio NRG CR total knee prosthesis. We compared the accuracy of component positioning measured using radiographs and CT scans, operating time and clinical outcome 1 year after surgery.

RESULTS

The mean hip-knee-ankle, frontal femoral and tibial component angle were 179.8° (ideally implanted 85%), 89.8° (88%), 90.4° (88%) respectively for the 3.1 group and 179.5° (96%), 90.6° (92%), 90.2° (94%) for the 4.0 group. The mean sagittal tibial component angle was 85.5° (82%) for the 3.1 group and 85.6° (92%) for the 4.0 group. The mean rotational femoral and tibial component angle were -0.5° (81%), -0.7° (73%) for the 3.1 group and 0.0° (84%), 0.4° (72%) for the 4.0 group. There were no statistically significant findings with regard to component positioning. Operating time was significantly longer in the 3.1 group (3.1 group: 137 min, 4.1group: 125 min, P < 0.01). No significant difference was detected in postoperative clinical outcome.

CONCLUSION

The navigation system update from Stryker 3.1 to Stryker 4.0 reduced operating time by 12 min. However, there were no statistically significant findings with regard to component positioning and clinical outcome.

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.

A prospective randomised controlled study of patient-specific cutting guides compared with conventional instrumentation in total knee replacement

Patient-specific cutting guides (PSCGs) are designed to improve the accuracy of alignment of total knee replacement (TKR). We compared the accuracy of limb alignment and component positioning after TKR performed using PSCGs or conventional instrumentation. A total of 80 patients were randomised to undergo TKR with either of the different forms of instrumentation, and radiological outcomes and peri-operative factors such as operating time were assessed. No significant difference was observed between the groups in terms of tibiofemoral angle or femoral component alignment. Although the tibial component in the PSCGs group was measurably closer to neutral alignment than in the conventional group, the size of the difference was very small (89.8° (sd 1.2) vs 90.5° (sd 1.6); p = 0.030). This new technology slightly shortened the bone-cutting time by a mean of 3.6 minutes (p < 0.001) and the operating time by a mean 5.1 minutes (p = 0.019), without tangible differences in post-operative blood loss (p = 0.528) or need for blood transfusion (p = 0.789). This study demonstrated that both PSCGs and conventional instrumentation restore limb alignment and place the components with the similar accuracy. The minimal advantages of PSCGs in terms of consistency of alignment or operative time are unlikely to be clinically relevant.

Surgeon variability in total knee arthroplasty component alignment: a Monte Carlo analysis

Component mal-alignment in total knee arthroplasty has been associated with increased revision rates and poor clinical outcomes. A significant source of variability in traditional, jig-based total knee arthroplasty is the performance of the surgeon. The purpose of this study was to determine the most sensitive steps in the femoral and tibia arthroplasty procedures. A computational model of the total knee arthroplasty procedure was created, and Monte Carlo simulations were performed that included surgeon variability in each step of the procedure. The proportion of well-aligned components from the model agrees with clinical literature in most planes. When components must be aligned within ±3° in all planes, component alignment was most sensitive to the accuracy of identifying the lateral epicondyle for the femoral component, and to the precision of the transverse plane alignment of the extramedullary guide for the tibial component. This model can be used as a tool for evaluating different procedural approaches or sources of variability to improve the quality of the total knee arthroplasty procedure.

A review of rapid prototyped surgical guides for patient-specific total knee replacement

Improvements in the surgical technique of total knee replacement (TKR) are continually being sought. There has recently been interest in three-dimensional (3D) pre-operative planning using magnetic resonance imaging (MRI) and CT. The 3D images are increasingly used for the production of patient-specific models, surgical guides and custom-made implants for TKR. The users of patient-specific instrumentation (PSI) claim that they allow the optimum balance of technology and conventional surgery by reducing the complexity of conventional alignment and sizing tools. In this way the advantages of accuracy and precision claimed by computer navigation techniques are achieved without the disadvantages of additional intra-operative inventory, new skills or surgical time. This review describes the terminology used in this area and debates the advantages and disadvantages of PSI.