Postoperative Mechanical Alignment Research Articles

Outcome in Total Knee Arthroplasty with a Medial-Lateral Balanced versus Unbalanced Gap

To evaluate the clinical outcome in 108 total knee arthroplasty (TKA) patients with a medial-lateral balanced versus unbalanced gap after a mean follow-up of 34 months. 64 women and 44 men (mean age, 69.5 years) underwent computer-assisted TKA for osteoarthritis using a cemented fixed-bearing cruciate-retaining prosthesis. The medial-lateral gap difference (measured with the prosthesis in situ and the patella reduced) was balanced (≤2 mm) in 81 patients and unbalanced (>2 mm) in 27 patients. After a mean follow-up of 34 months, patients were assessed using the Western Ontario and McMaster Universities Arthritis Index (WOMAC) questionnaire for pain, stiffness, and physical function. Scores were normalised to 0% (worst) to 100% (best). The balanced and unbalanced gap groups were comparable in terms of age, severity of osteoarthritis, and proportion of pre- and post-operative mechanical alignment. Compared with the balanced gap group, the unbalanced gap group had a larger medial-lateral extension gap difference (0.75±0.57 vs. 2.02±1.15 mm, p=0.001) and medial-lateral flexion gap difference (0.79±0.63 vs. 2.98±2.13 mm, p=0.001) and lower normalised total WOMAC score (84.9±18 vs. 74.8±20.8, p=0.017). WOMAC score is better in TKAs with a medial-lateral balanced (<2 mm) gap.

Radiographic outcomes in the coronal plane with iASSIST™ versus optical navigation for total knee arthroplasty: A preliminary case-control study

BackgroundThe new navigation system iASSIST™ for total knee arthroplasty (TKA) relies on accelerometers and gyroscopes. The objective of this prospective study was to compare the accuracy of iASSIST™ to that of the conventional optical navigation system Navitrack™ by determining the rate of mechanical axis restoration (±3°), postoperative mean mechanical alignment, rate of adequate femoral and tibial component positioning, mean operative time, and occurrence of navigation-related adverse events. HypothesisThe rate of mechanical axis restoration (±3°) is not lower with iASSIST™ than with the conventional navigation system Navitrack™. Material and methodsOf 40 patients who underwent primary TKA between October 2013 and March 2014, 20 had navigation using iASSIST™ and 20 using Navitrack™. Six months after TKA, an independent observer measured three parameters on coronal radiographs: the hip-knee-ankle angle (HKA), the mechanical lateral distal femoral angle (mLDFA), and the mechanical medial proximal tibial angle (mMPTA). ResultsThe two groups showed no significant differences for the rates of HKA restoration (P=0.3), adequate coronal positioning of the femoral component (P=0.12) and tibial component (P=0.12), or optimal success (P=0.09). Significant differences in favour of iASSIST™ were demonstrated for the values and angular deviations of the HKA (P=0.02) and mMPTA (P=0.01), whereas no significant difference was found for mLDFA. There were no significant differences regarding the mean operative time (P=0.06) or the occurrence of navigation-related adverse events (P=0.18). DiscussionThe iASSIST™ system provides a neutral mechanical axis and optimal component position in the coronal plane in 95% of cases, indicating that it is as accurate as the optical navigation system Navitrack™. Level of evidenceIII, prospective case-control study.

Measuring long radiographs affects the positioning of femoral components in total knee arthroplasty: a randomized controlled trial.

The aim of this study was to investigate if preoperative measurements of the femoral valgus angle (FVA) affected the mechanical alignment, individual component positions and clinical outcome in total knee arthroplasty (TKA). 120 patients were randomized into two groups. In one group (control), a fixed FVA for the intramedullary femoral guide was set at 7°, whereas in the other group (measured) FVA was measured preoperatively on long hip-knee-ankle radiographs, and the angle for the distal femoral cut was set accordingly. Preoperatively and 1year after TKA, range of motion (ROM) and Knee Society Score (KSS) were assessed. Postoperatively, the coronal alignments of the components and the mechanical alignment were measured comparing the rate of outliers which deviated more than 3° from the neutral mechanical axis. 104 patients remained for the radiological analysis (52 in each group). There were no significant differences either in the mean preoperative or postoperative mechanical alignment, or femoral or tibial component alignment; also, there were no differences in the number of postoperative mechanical axis or tibial component alignment outliers. However, the number of femoral component alignment outliers was significantly higher in the control group. 97 patients were available for clinical outcome analysis. Preoperatively, the groups did not differ significantly with respect to KSS or ROM. The postoperative ROM and KSS functional subscale scores were similar between the groups. However, there was slightly but significantly better postoperative KSS objective subscale score in the measured group. Preoperative FVA measurement and following femoral distal cut adjustments did not affect overall leg alignment postoperatively, while positioning of femoral component was improved together with minor improvements in objective KSS subscale scores.

Handheld Navigation Device and Patient-Specific Cutting Guides Result in Similar Coronal Alignment for Primary Total Knee Arthroplasty: a Retrospective Matched Cohort Study.

Proper alignment of total knee arthroplasty (TKA) is essential for TKA function and may reduce the risk of aseptic failure. Technologies that prevent malalignment may reduce the risk of revision surgery. The purpose of this study was to compare two competing TKA systems that purport improved alignment: patient-specific instrumentation (PSI), and a handheld portable navigation device (NAV). After IRB approval, 49 consecutive PSI TKAs (40 patients) were matched based on preoperative characteristics to 49 NAV TKAs (40 patients) performed by a single surgeon. A blinded observer measured alignment on digital radiographs. Operating room records were reviewed for procedure times. Two-tailed paired sample t tests and McNemar's test were used as appropriate. Alpha level was 0.05 for all tests. Preoperative cohort characteristics were not different. Mean postoperative long-leg mechanical alignment was within ±1° of neutral for both groups, although statistically different (p = 0.026). There were no other significant differences in coronal alignment. PSI exhibited significantly greater posterior tibial slope (4.4°) compared to NAV (2.7°) (p = 0.004); PSI resulted in significantly more outliers (>6°; p = 0.004). Procedure time for unilateral TKAs was lower for PSI (74.4min) compared to that for NAV (80.6min; p = 0.023). NAV and PSI technologies provided excellent coronal plane alignment. NAV was better for sagittal tibial slope, while PSI procedure times were shorter for unilateral TKA. The impact of these technologies on patient-reported outcomes and TKA survivorship is controversial and should be the focus of future research.

Predictors of Subjective Outcome After Medial Unicompartmental Knee Arthroplasty

BackgroundUnexplainable pain after medial unicompartmental knee arthroplasty (UKA) remains a leading cause for revision surgery. Therefore, the aim of this study is to identify the patient-specific variables that may influence subjective outcomes after medial UKA to optimize results. MethodsRetrospectively, we analyzed 104 consecutive medial UKA patients. The evaluated parameters consisted of age, body mass index, gender, preoperative radiographic severity of the various knee compartments, and preoperative and postoperative mechanical axis alignments. ResultsAt an average of 2.3-year follow-up, our data demonstrate that body mass index, gender, and preoperative severity among the various knee compartments do not influence Western Ontario and McMaster Universities Arthritis Index (WOMAC) results. Preoperatively, patients aged <65 years had inferior WOMAC stiffness (4.6 vs 2.9, P = .001), pain (9.7 vs 7.6, P = .041), and total (37.2 vs 47.6, P = .028) scores vs patients aged ≥65 years. Postoperatively, only the difference on the WOMAC stiffness subscale remained significant between both age groups, in favor of patients aged ≥65 years (1.0 vs 1.5, P = .035). A postoperative varus mechanical axis alignment of 1°-4° correlated to significantly superior WOMAC pain (P = .03), function (P = .04), and total (P = .04) scores compared to a varus of ≤1° or ≥4°. ConclusionOur data suggest that greater pain relief can be expected in patients aged <65 years and that a postoperative lower limb alignment of 1°-4° varus should be pursued. Taking these factors into consideration will help to maximize clinical outcomes, fulfill patient expectations after medial UKA, and subsequently minimize revision rates.

Computerized tomography based "patient specific blocks" improve postoperative mechanical alignment in primary total knee arthroplasty.

To compare the postoperative mechanical alignment achieved after total knee arthroplasty (TKA) using computer tomography (CT) based patient specific blocks (PSB) to conventional instruments (CI). Total 80 knees were included in the study, with 40 knees in both the groups operated using PSB and CI. All the knees were performed by a single surgeon using the same cruciate sacrificing implants. In our study we used CT based PSB to compare with CI. Postoperative mechanical femoro-tibial angle (MFT angle) was measured on long leg x-rays using picture archiving and communication system (PACS). We compared mechanical alignment achieved using PSB and CI in TKA using statistical analysis. The PSB group (group 1) included 17 females and seven males while in CI group (group 2) there were 15 females and eight males. The mean age of patients in group 1 was 60.5 years and in group 2 it was 60.2 years. The mean postoperative MFT angle measured on long-leg radiographs in group 1 was 178.23° (SD = 2.67°, range: 171.9° to 182.5°) while in group 2, the mean MFT angle was 175.73° (SD = 3.62°, range: 166.0° to 179.8°). There was significant improvement in postoperative mechanical alignment (P value = 0.001), in PSB group compared to CI. Number of outliers were also found to be less in group operated with PSB (7 Knee) compared to those operated with CI (17 Knee). PSB improve mechanical alignment after total knee arthroplasty, compared to CI. This may lead to lower rates of revision in the PSB based TKA as compared to the conventional instrumentation.

Postoperative Mechanical Axis Alignment and Components Position after Conventional and Patient-Specific Total Knee Arthroplasty

Introduction: Accurate postoperative alignment and implant positioning are determinant factors for successful total knee arthroplasty (TKA). Patient-specific template (PST) is a technique that uses computer technology for the planning, deigning and production of cutting guides. This study aims to compare PST to conventional technique in terms of mechanical axis alignment and component positioning. Patients and method: 109 TKA were performed for 78 patients in 2 groups. Group A included 69 conventional TKA in 55 patients and Group B included 40 patient-specific TKA in 23 patient. Postoperative long-film X-rays were done for all patients to observe the mechanical axis, anatomical axis, lateral distal femoral mechanical angle and medial proximal tibial angle. Results: No statistically significant difference was found between the two groups regarding alignment or component positioning. Conclusion: Both techniques have shown similar results in restoring the mechanical axis and alignment after TKA. However, PST had the advantages of reduced blood loss and shorter operative time.

Postoperative mechanical alignment of the lower limb corresponding to the successful clinical outcome after total knee arthroplasty (TKA)

Postoperative mechanical alignment of the lower limb corresponding to the successful clinical outcome after total knee arthroplasty (TKA)

Postoperative Coronal Alignment After Total Knee Arthroplasty: Does Tailoring the Femoral Valgus Cut Angle Really Matter?

Postoperative alignment was measured in 80 TKA divided into 2 groups. Knees in the tailored group (n=40) were performed with a personalized valgus cut angle (VCA) based on preoperative hip-to-ankle (HTA) radiographs. The fixed group knees (n=40) were performed utilizing a 4° VCA in valgus knees and obese patients, and 5° in neutral and varus knees. There was no significant difference between groups in average preoperative mechanical alignment or average severity of preoperative deformity. There was no statistically significant difference between groups in postoperative mechanical alignment (tailored: 2.6°; fixed: 1.3°; P=0.08) or severity of residual deformity (tailored: 3.5°; fixed: 2.6°; P=0.10). Accuracy of the tibial cut angle (TCA) and severity of the preoperative deformity were strong independent predictors of postoperative alignment (R2=58% and R2=33%, respectively).

Minor varus alignment provides better results than neutral alignment in medial UKA

IntroductionFew data exist regarding the outcome and survivorship of medial UKA in patients with minor varus alignment. The purpose of this study was therefore to analyse the clinical results of medial UKA implanted with no more than 7° of varus, and to verify whether there was a relationship between limb alignment and overall outcomes. Material and methodsOne hundred and twenty five medial fixed-bearing UKAs with no more than 7° of varus were retrospectively analysed. The varus/valgus inclination and thickness of the bone cuts were performed relating to the proximal tibial epiphyseal axis. Patients were assessed with the IKS scores and range of knee motion. The subjects were classified into three groups according to the postoperative femoro-tibial mechanical alignment angle (group A: −2° to 1°; group B: 2° to 4°; group C: 5° to 7°). ResultsThe mean follow-up was 7.6years (range, 3.5–9.3). IKS knee scores increased proportionally with increasing varus according to a linear relationship (p≪0.01). Additionally, IKS knee scores were significantly higher in group B and still higher in group C if compared to those in group A (p=0.003). Finally, a significantly higher frequency of IKS function scores>90 points in subjects with femoro-tibial mechanical alignment angle≥4° was found (p=0.009). ConclusionsMinor varus alignment does not compromise the mid- to long-term outcome of a medial UKA, and gives better results compared to neutral or close-to-neutral alignment. Level of evidenceIV — Retrospective case series study.

Hip–Knee–Ankle Radiographs Are More Appropriate for Assessment of Post-Operative Mechanical Alignment of Total Knee Arthroplasties than Standard AP Knee Radiographs

Weight-bearing hip–knee–ankle (HKA) radiographs are the gold standard for measuring lower limb alignment after total knee arthroplasty (TKA), however the majority of UK units use standardised anteroposterior (AP) knee radiographs. This study aimed to determine whether standardised AP knee radiographs adequately assess lower limb alignment after TKA. HKA radiographs from 50 post-operative TKAs were cropped to the size of a standardised AP knee radiograph allowing comparison of mechanical and anatomical alignment measurements between the two views. Repeatability of alignment measurements was significantly better for HKA radiographs, however, there was poor agreement of the mechanical alignment measured between the two views. Standardised AP knee radiographs are insufficient to assess the mechanical alignment of post-operative TKA and we recommend routinely using HKA radiographs.

Outcomes and survivorship of unicondylar knee arthroplasty in patients with severe deformity.

Fifty-three patients with severe deformity (40 patients with FFD ≥15° and 13 patients with varus deformity ≥15°, Group A) were matched with 53 patients with less severe deformities who underwent UKA (Group B/controls) in terms of age, sex, BMI and duration of follow-up. Their flexion range, Knee Society scores (KSS), Oxford knee scores (OKS) and SF-36 QOL scores were analysed pre-operatively and at 2years. Group A patients were largely similar to Group B patients pre-operatively in terms of maximum flexion angle, OKS and SF-36 scores except for knee score and mental health component of SF-36. At 2years, Group A reported largely similar results compared with Group B in all outcome scores (OKS, KSS, SF-36) and flexion angle. Post-operative mechanical alignment was better for the control group though it is not statistically significant. There were no revisions in the patients with severe pre-operative deformity at 5years post-operatively. (Survivorship 100% at 5years). Selected patients with severe deformity can achieve good function and QOL with UKA if satisfactory mechanical alignment is restored. This study supports a broadening of the indications of UKA; however, further follow-up is needed to assess the longer-term durability of the operation. IV.

Early experiences with robot-assisted total knee arthroplasty using the DigiMatch™ ROBODOC® surgical system.

The use of robotics in total knee arthroplasty (TKA) has been shown to minimise human error, as well as improve the accuracy and precision of component implantation and mechanical axis alignment. The present study aimed to demonstrate that robot-assisted TKA using ROBODOC® is safe and capable of producing a consistent and accurate postoperative mechanical axis. We prospectively recruited 27 consecutive patients who underwent robot-assisted TKA between May and December 2012. Two patients were excluded from the study due to intraoperative technical problems with the robot. Long-leg radiography and computed tomography were performed prior to surgery, and used for mechanical axis measurements and component sizing. DigiMatch™ ROBODOC® Surgical System software version 4.3.6 (Curexo Technology Corp, Fremont, CA, USA) was used in all cases to perform bone cuts in accordance with the preoperative plan. The postoperative coronal mechanical alignment was within 3 degrees, with a mean alignment of -0.4 ± 1.7 degrees, confirming the accuracy of the preoperative surgical plan and bone cuts. The mean operating time was 96 ± 15 min, and preoperative planning yielded 100% implant sizing accuracy. Robotics has the potential to enable surgeons to consistently attain ideal postoperative alignment. The use of bone movement monitors and an integrated navigation system enhances the safety profile of ROBODOC® by minimising errors. However, the role of the surgeon in TKA is still vital, as the surgeon is ultimately in charge of planning the surgery, its execution and ensuring soft tissue balance during TKA.

Total knee arthroplasty in patients with substantial deformities using primary knee components.

Although advocated for severe varus and valgus deformities, constrained implant designs are associated with a number of disadvantages in total knee arthroplasty (TKA). Combining a minimally invasive surgical approach with an interchangeable posterior stabilized (PS) implant design may allow adequate soft tissue balancing with a minimal amount of constraint and without residual instability. Retrospectively 51 patients operated with the minimally invasive far medial subvastus approach for severe varus or valgus deformity, who underwent primary TKA with a fully interchangeable PS implant (Vanguard, Biomet Inc., Warsaw IN, USA) between 2009 and 2013 were examined. Soft tissue releases was performed using a piecrust needling technique. Preoperative alignment and surgical parameters were collected for all patients. All patients underwent preoperative and follow-up radiographic assessment and completed a battery of clinical assessments. All procedures were performed successfully, with alignment improving from a preoperative mean (SD) varus deformity of 165° (3°) and a mean (SD) valgus deformity of 196° (4.5°) to an overall mean (SD) postoperative mechanical alignment of 179.5° (3.0°). Nine patients had postoperative varus, while three patients had a postoperative valgus deviation from neutral alignment >3°. The mean change in joint line position in extension was -0.0 ± 0.6 mm. Clinical scores at final follow-up were excellent for both groups. Good TKA outcomes can be achieved in patients with substantial varus or valgus deformities using a combination of a minimally invasive far medial subvastus approach, interchangeable PS implants and soft tissue releases with a piecrust needling technique. III.

Effect of high tibial osteotomy on joint loading in symptomatic patients with varus aligned knees: a study using SPECT/CT.

The purpose was to prospectively evaluate the outcome, in particular the SPECT/CT bone tracer uptake (BTU) after high tibial osteotomy (HTO) due to symptomatic varus malalignment. It was the hypothesis that the BTU after HTO decreases in the medial compartment, clinical outcome and the degree of correction correlates with BTU and asymptomatic patients after HTO reveals a significantly decreased BTU in the medial subchondral areas. Twenty-two consecutive patients with 23 knees undergoing medial opening-wedge HTO for medial compartment overloading were assessed pre- and postoperatively (12 and/or 24months) using Tc-99m-HDP-SPECT/CT including our 4D-SPECT/CT protocol. BTU was quantified and localized to specific biomechanically relevant joint areas. Maximum absolute and relative values (mean±standard deviation, median and range) for each area were recorded. Pre- and postoperative mechanical alignment was measured. At 24months after HTO, the WOMAC score was used. A significant decrease of BTU in the medial subchondral zones after HTO was found (preoperatively to 12 and 24months postoperatively, p<0.01). BTU normalized in all asymptomatic patients within 24months. This decrease was partly seen in the lateral compartments, but significantly higher in the medial compartments (p<0.0001). A significant increase of the BTU was noted in zones directly adjacent to the plate or within the osteotomy zone (p<0.01). Decreased BTU was observed in osteotomy zones at 24months postoperatively following higher uptake values at 12months postoperatively. The average valgus correction of the tibiofemoral angle was 5.9°±2.8°. Less stiffness correlated significantly with a higher decrease in BTU (p<0.05). Higher postoperative BTU significantly correlated with more pain (p<0.05). No statistical significant associations between BTU and alignment correction were found. In patients with medial compartment, overloading due to varus malalignment HTO led to a significant decrease in BTU in the medial joint compartments. SPECT/CT BTU patterns and intensity in these patients pre- to 12 and 24months postoperatively were seen. These correlated significantly with pain and stiffness. Hence, SPECT/CT could be used for assessment of adequate correction and healing after HTO. SPECT/CT could be further used to identify the optimal individualized correction for each patient and clinical scenario. Diagnostic prospective study, Level II.

Computer-navigated minimally invasive total knee arthroplasty for patients with retained implants in the femur

Total knee arthroplasty (TKA) in patients with knee arthritis and retained implants in the ipsilateral femur is a challenge for knee surgeons. Use of a conventional intramedullary femoral cutting guide is not practical because of the obstruction of the medullary canal by implants. Previous studies have shown that computer-assisted surgery (CAS) can help restore alignment in conventional TKA for patients with knee arthritis with retained femoral implants or extra-articular deformity, without the need for implant removal or osteotomy. However, little has been published regarding outcomes with the use of navigation in minimally invasive surgery (MIS)-TKA for patients with this complex knee arthritis. MIS has been proven to provide less postoperative pain and faster recovery than conventional TKA, but MIS-TKA in patients with retained femoral implants poses a greater risk in limb malalignment. The purpose of this study is to report the outcome of CAS-MIS-TKA in patients with knee arthritis and retained femoral implants. Between April 2006 and March 2008, eight patients with knee arthritis and retained femoral implants who underwent the CAS-MIS-TKA were retrospectively reviewed. Three of the eight patients had extra-articular deformity, including two femur bones and one tibia bone, in the preoperative examination. The anteroposterior, lateral, and long-leg weight-bearing radiographs carried out at 3-month follow-up was used to determine the mechanical axis of lower limb and the position of components. The mean preoperative femorotibial angle in patients without extra-articular deformity was 3.8° of varus and was corrected to 4.6° of valgus. With the use of navigation in MIS-TKA, the two patients in this study with extra-articular femoral deformity also obtained an ideal postoperative mechanical axis within 2° of normal alignment. Overall, there was a good restoration of postoperative mechanical alignment in all cases, with a mean angle of 0.4° of varus. No limb malalignment or component malposition was found. In clinical assessments, there were also significant improvements in knee specific scores, functional scores, and motion arc. The results of this study suggest that navigation can help achieve accurate alignment and proper prosthesis positioning in MIS-TKA for patients with retained femoral implants and for whom intramedullary rod guidance is impractical.

Patient-Specific Instrumentation Does Not Improve Alignment in Total Knee Arthroplasty

Patient-specific instrumentation (PSI) was developed to improve the accuracy of component positioning in total knee arthroplasty (TKA). A meta-analysis of level I and level II studies was performed to determine if PSI improves the mechanical alignment of the leg compared with conventional instrumentation (CI) in TKA. Seven studies met inclusion criteria evaluating 559 patients undergoing TKA. Mean coronal alignment was within 1 degree of neutral mechanical alignment in both groups (PSI, 0.78 degrees; CI, 0.81 degrees). There were fewer outliers in the PSI group (21.1%) than in the CI group (23.2%), but this was not statistically significant (p = 0.59). On the basis of the data from this analysis, PSI does not significantly improve the postoperative mechanical alignment of the limb after TKA. Moreover, PSI does not decrease the number of outliers compared with CI.

The effect of inferomedial screw on postoperative shoulder function and mechanical alignment in proximal humerus fractures

The aim of the study was to evaluate the clinical and radiologic results of locking plate fixation with or without inferomedial screw (IMS) in surgically treated proximal humerus fractures. Thirty-six patients with displaced proximal humerus fractures from two centers were operated using locking plate. All of the fractures were classified according to the Neer classification. In 18 of the cases, an additional IMS running through the medial curvature of the surgical neck was used. There was no significant difference among both groups in terms of height, gender, weight, and mechanism of injury. The fractures were evaluated according to the radiographic and functional findings during follow-up period of 14 months in average (range 8-32 months). At the end of first year, shoulder radiographs were received and shoulder examinations were performed using ASES scores. Humeral head-shaft angles were measured by true AP projections. Head-shaft angle measurements were categorized as varus if <125, normal if between 125 and 145, and valgus if >145. Mean time for fracture healing was 18 weeks. Complete union was achieved in 35 patients by the end of 6 months. In one of the 18 displaced proximal humerus fractures of IMS (+) group, the head-shaft angle was measured to be <125, whereas six patients had varus deviation in IMS (-) group at follow-up (p < 0.05). Mean ASES scores of IMS (+) group and IMS (-) group were 58.21 ± 5.82 and 38.61 ± 3.44, respectively (p < 0.001). Use of inferomedial screw running through the medial curvature of surgical neck prevents varus deformity and improves functional outcome after surgical treatment for proximal humerus fractures.

Assessment of the loading history of patients after high tibial osteotomy using SPECT/CT - a new diagnostic tool and algorithm

BackgroundSingle photon emission computerized tomography and conventional computerized tomography (SPECT/CT) tracer uptake has been shown to reflect the loading history of the tibiofemoral knee joint and correlate with the mechanical and anatomical alignment. It was our primary purpose to develop a novel standardized SPECT/CT algorithm for patients undergoing high tibial osteotomy, evaluate the inter- and intra-observer reliability (OR), and assess the clinical applicability for follow-up of patients before and after high tibial osteotomy.MethodsThe localization scheme defines 9 femoral, 8 patellar, and 13 tibial zones to accurately map the examined tracer uptake volume in each anatomical area of interest. Maximum values for each area (mean ± standard deviation, median, and range) of the localization scheme were recorded as well as normalized values for the intensity of SPECT/CT tracer uptake calculated. The inter- and intra-OR was assessed for SPECT/CT localization and tracer activity. Pre- and postoperative mechanical alignment was assessed in SPECT/CT using a custom-made specialized software. The median inter- and intra-observer differences of the measured mechanical alignment were calculated along with the inter- and intra-OR.ResultsThe localization scheme showed near-perfect inter- and intra-OR (intra-class correlation coefficient (ICC) > 0.9) for the measurement of tracer activity and localization in all anatomical regions. For measurements of mechanical alignment, there was a strong agreement between the two observers (an inter-OR of ICC = 0.99 and an intra-OR of ICC = 0.98).ConclusionsThe presented SPECT/CT algorithm is highly reliable and clinically feasible. Combined with mechanical alignment analysis, it provides the surgeon with helpful information about realignment effects of high tibial osteotomies (HTOs) and might help identify the optimal personalized degree of correction in HTO surgery.

Computer-assisted navigation for cruciate-retaining total knee arthroplasty in patients with advanced valgus arthritic knees

BackgroundThe valgus arthritic knee is a complex deformity involving both soft tissue and bony problems that significantly affect the positioning of the components for, and decrease the accuracy of, reconstructed alignment in total knee arthroplasty (TKA). The unique bony deformity and soft tissue problem makes the use of conventional mechanical instrumentation difficult and leads to unsatisfactory results. PurposeThe purpose of this study was to investigate the effect of computer-assisted navigation for TKA on the postoperative mechanical axis, component alignment, and functional outcomes in the arthritic knee with genu valgus deformity. MethodsFrom January 2003 to August 2009, 24 patients (24 knees) with advanced valgus knee arthritis who underwent computer-assisted navigation for cruciate-retaining TKA were retrospectively reviewed. The accuracy of the postoperative mechanical axis and component alignment, and functional outcomes were assessed. ResultsThe mean postoperative mechanical axis was 180.2° (range, 178.1–182.5°). All patients achieved the targeted goal of a leg axis within 3° of the neutral axis. The joint line was not substantially elevated. No patient required conversion to a constrained component to achieve stability. At a mean follow-up of 45.5 months, the Hospital for Special Surgery (HSS) knee score improved from a mean preoperative score of 55.6 to 92.8 postoperatively. The International Knee Society (IKS) clinical score improved from 42.2 to 95.9. The IKS for pain improved from 15.4 to 47.1, and the IKS knee function score improved from 35.8 to 95.4. ConclusionComputer-assisted navigation for TKA is a useful alternative technique for advanced valgus knee arthritis where accurate restoration of the joint line, proper alignment of the limb and prosthetic components, and meticulous soft tissue balancing may be challenging because of bony deformities and soft tissue contractures.