Nanne P. Kort

Preliminary experience with the patient-specific templating total knee arthroplasty 40 cases compared with a matched control group

Background and purpose Patient-specific templating total knee arthroplasty (TKA) is a new method for alignment of a total knee arthroplasty that uses disposable guides. We present the results of the first 40 consecutive patients who were operated on using this technique. Methods In this case-control study, we compared blood loss, operation time, and alignment of 40 TKAs performed using a patient-specific templating alignment technique with values from a matched control group of patients who were operated on by conventional intramedullary alignment technique. Alignment of the mechanical axis of the leg and flexion/extension and varus/valgus of the individual prosthesis components were measured on standing, long-leg, and standard lateral digital radiographs. The fraction of outliers (> 3˚) was determined. Results Mean mechanical axis of templating TKAs was 181° with a fraction of outliers of 0.3, and mean mechanical axis of conventional TKAs was 179˚ (outlier fraction 0.5). Fraction of outliers in the frontal plane for femoral components was 0.05 in the templating TKAs and 0.4 in the conventional TKAs, and for tibial components the corresponding values were 0.2 and 0.2. In the templating TKAs and conventional TKAs, fraction of outliers in the sagittal plane was 0.4 and 0.9, respectively, for femoral components and 0.4 and 0.6 for tibial components. Mean operation time was 10 min shorter and blood loss was 60 mL less for templating TKA than for intramedullary-aligned TKAs. Interpretation Patient-specific templating TKA showed improved accuracy of alignment and a small reduction in blood loss and operating time compared to intramedullary-aligned TKA, but the fraction of outliers was relatively high. Larger RCTs are needed for further evaluation of the technique and to define the future role of patient-specific template alignment techniques for TKA.

Long-term Follow-up of a Randomized Controlled Trial Comparing Scarf to Chevron Osteotomy in Hallux Valgus Correction

Background: Hallux valgus is one of the most common foot deformities. This long-term follow-up study compared the results of 2 widely used operative treatments for hallux valgus: the scarf and chevron osteotomy. Methods: Conventional weight bearing anteroposterior (AP) radiographs of the foot were made for evaluating the intermetatarsal angle and hallux valgus angle. For clinical evaluation, the American Orthopaedic Foot & Ankle Society (AOFAS) rating system for the hallux metatarsophalangeal-interphalangeal scale was used together with physical examination of the foot. These data were compared with the results from the original study. The Short Form 36 questionnaire, the Manchester-Oxford Foot Questionnaire (MOXFQ), and a general questionnaire including a visual analog scale (VAS) pain score were used for subjective evaluation. The primary outcome measures were the radiologic recurrence of hallux valgus and reoperation rate of the same toe. Secondary outcome measures were the results from the radiographs and subjective and clinical evaluation. The response rate was 76% at the follow-up of 14 years; in the chevron group, 37 feet were included compared with 36 feet in the scarf group. Results: Twenty-eight feet in the chevron group and 27 in the scarf group developed recurrence of hallux valgus (P = .483). One patient in the scarf group had a reoperation of the same toe compared with none in the chevron group (P = .314). Current VAS pain scores and results from the SF-36, MOXFQ, and AOFAS did not significantly differ between groups. Conclusion: Both techniques showed similar results after 2 years of follow-up. At 14 years of follow-up, neither technique was superior in preventing recurrence. Level of Evidence: Level II, randomized controlled trial.

Patient-specific guide for revision of medial unicondylar knee arthroplasty to total knee arthroplasty: Beneficial first results of a new operating technique performed on 10 patients

Background and purpose Unicompartmental to total knee arthroplasty revision surgery can be technically demanding. Joint line restoration, rotation, and augmentations can cause difficulties. We describe a new technique in which single-way fitting guides serve to position the knee system cutting blocks. Method Preoperatively, images of the distal femur and proximal tibia are taken using CT scanning. These images are used to create a patient-specific guide that fits in one single position on the contours of the bone and the prosthesis in situ. The guides are fixed with pins and then removed. The pins determine the position of the cutting blocks. 10 consecutive revisions were performed using this technique. Results All guides fitted well. 7 of 10 femoral prostheses were within the desired AP and sagittal angle ± 3°. However, 1 proximal tibia did not have enough bone stock on the medial plateau for adequate fixation of the guide, so conversion to intramedular referencing was performed. This was to be expected after the preoperative planning. All tibial components were within the desired AP angle ± 3° and 7 of 10 were within the desired sagittal angle. Hip-knee-ankle angle was within 0 ± 3° in 8 of 10 cases. Interpretation This new technique makes preoperative planning and execution of this plan during surgery less demanding. Problems such as the need for augmentations can be predicted at the preoperative planning. The instrumentation must be redesigned in order to make this technique work in cases where there is minimal bone stock present.

No radiographic difference between patient-specific guiding and conventional Oxford UKA surgery

PurposeImplant position is an important factor in unicompartmental knee arthroplasty (UKA) surgery. Results on conventional UKA alignment are commonly described in literature. Patient-specific guiding (PSG) is a new technique for positioning the Oxford UKA. Our hypothesis is that PSG improves component position without affecting the HKA angle.MethodsThis prospective study compares the results of our first thirty cases of cementless Oxford UKA using PSG with thirty cases using conventional outlining. Baseline characteristics for both groups were identical. Details on handling of the guide, estimated blood loss and operation time were recorded. Postoperative screened radiographs and standing long-leg radiographs of both groups were compared.ResultsMedian AP position of the femoral component was 3 degrees varus (−5 to 9) using PSG versus 2 degrees varus (−10 to 8) for the conventional group. For the femoral flexion, this was 9 degrees flexion (0–16) using PSG versus 12 degrees flexion (0–20). The tibial median AP position was 1 degree varus (−3 to 7) using PSG versus 2 degrees varus (−5 to 10). The median tibial posterior slope was 5 degrees (1–10) using PSG versus 5 degrees (0–12). All guides aligned well. No conversion to conventional outlining was performed, and no significant changes had to be made to the original approved plan. Operation time, estimated blood loss and postoperative haemoglobin drop were not significantly different between both groups.DiscussionImplant position was not different between both groups, even in the early phase of the learning curve. Perioperative results were not different between both groups.Level of evidenceIII.

Patient-specific positioning guides for total knee arthroplasty: no significant difference between final component alignment and pre-operative digital plan except for tibial rotation

AbstractPurposeTo assess whether there is a significant difference between the alignment of the individual femoral and tibial components (in the frontal, sagittal and horizontal planes) as calculated pre-operatively (digital plan) and the actually achieved alignment in vivo obtained with the use of patient-specific positioning guides (PSPGs) for TKA. It was hypothesised that there would be no difference between post-op implant position and pre-op digital plan.Methods Twenty-six patients were included in this non-inferiority trial. Software permitted matching of the pre-operative MRI scan (and therefore calculated prosthesis position) to a pre-operative CT scan and then to a post-operative full-leg CT scan to determine deviations from pre-op planning in all three anatomical planes.ResultsFor the femoral component, mean absolute deviations from planning were 1.8° (SD 1.3), 2.5° (SD 1.6) and 1.6° (SD 1.4) in the frontal, sagittal and transverse planes, respectively. For the tibial component, mean absolute deviations from planning were 1.7° (SD 1.2), 1.7° (SD 1.5) and 3.2° (SD 3.6) in the frontal, sagittal and transverse planes, respectively. Absolute mean deviation from planned mechanical axis was 1.9°. The a priori specified null hypothesis for equivalence testing: the difference from planning is >3 or <−3 was rejected for all comparisons except for the tibial transverse plane.ConclusionPSPG was able to adequately reproduce the pre-op plan in all planes, except for the tibial rotation in the transverse plane. Possible explanations for outliers are discussed and highlight the importance for adequate training surgeons before they start using PSPG in their day-by-day practise.Level of evidenceProspective cohort study, Level II.

Patient specific guides for total knee arthroplasty are ready for primetime.

AIM To present the radiological results of total knee arthroplasty (TKA) with use of patient specific matched guides (PSG) from different manufacturer in patients suffering from severe osteoarthritis of the knee joint. METHODS This study describes the results of 57 knees operated with 4 different PSG systems and a group operated with conventional instrumentation (n = 60) by a single surgeon. The PSG systems were compared with each other and subdivided into cut- and pin PSG. The biomechanical axis [hip-knee-ankle angle (HKA)], varus/valgus of the femur [frontal femoral component (FFC)] and tibia (frontal tibial component) component, flexion/extension of the femur [flexion/extension of the femur component (LFC)] and posterior slope of the tibia [lateral tibial component (LTC)] component were evaluated on long-leg standing and lateral X-rays. A percentage of > 3(°) deviation was seen as an outlier. RESULTS The inter class correlation coefficient (ICC) revealed that radiographic measurements between both assessors were reliable (ICC > 0.8). Fisher exact test was used to test differences of proportions. The percentage of outliers of the HKA-axis was comparable between both the PSG and conventional groups (12.28% vs 18.33%, P < 0.424) and the cut- and pin PSG groups (14.3% vs 10.3%, P < 1.00). The percentage of outliers of the FFC (0% vs 18.33%, P < 0.000), LFC (15.78% vs 58.33%, P < 0.000) and LTC (15.78% vs 41.67%, P < 0.033) were significant different in favour of the PSG group. There were no significant differences regarding the outliers between the individual PSG systems and the PSG group subdivided into cut- and pin PSG. CONCLUSION PSG for TKA show significant less outliers compared to the conventional technique. These single surgeon results suggest that PSG are ready for primetime.

Inter-observer reliability of measurements performed on digital long-leg standing radiographs and assessment of validity compared to 3D CT-scan

BACKGROUND Long-leg radiographs (LLR) are often used in orthopaedics to assess limb alignment in patients undergoing total knee arthroplasty (TKA). However, there are still concerns about the adequacy of measurements performed on LLR. We assessed the reliability and validity of measurements on LLR using three-dimensional computed tomography (3D CT)-scan as a gold standard. METHODS Six different surgeons measured the mechanical axis and position of the femoral and tibial components individually on 24 LLR. Intraclass correlation coefficients (ICC) were calculated to obtain reliability and Bland-Altman plots were constructed to assess agreement between measurements on LLR and measurements on 3D CT-scan. RESULTS ICC agreement for the six observer measurements on LLR was 0.70 for the femoral component and 0.80 for the tibial component. The mean difference between measurements performed on LLR and 3D CT-scan was 0.3° for the femoral component and -1.1° for the tibial component. Variation of the difference between LLR and 3D CT-scan for the femoral component was 1.1° and 0.9° for the tibial component. 95% of the differences between measurements performed on LLR and 3D CT-scan were between -1.9 and 2.4° (femoral component) and between -2.9 and 0.7 (tibial component). CONCLUSION Measurements on LLR show moderate to good reliability and, when compared to 3D CT-scan, show good validity. CLINICAL TRIAL REGISTRATION NUMBER institutional review board Atrium-Orbis-Zuyd, number: 11-T-15. LEVEL OF EVIDENCE Prospective cohort study, Level II.

A radiological analysis of the difference between MRI- and CT-based patient-specific matched guides for total knee arthroplasty from the same manufacturer: a randomised controlled trial.

AIMS This prospective randomised controlled trial was designed to evaluate the outcome of both the MRI- and CT-based patient-specific matched guides (PSG) from the same manufacturer. PATIENTS AND METHODS A total of 137 knees in 137 patients (50 men, 87 women) were included, 67 in the MRI- and 70 in the CT-based PSG group. Their mean age was 68.4 years (47.0 to 88.9). Outcome was expressed as the biomechanical limb alignment (centre hip-knee-ankle: HKA-axis) achieved post-operatively, the position of the individual components within 3° of the pre-operatively planned alignment, correct planned implant size and operative data (e.g. operating time and blood loss). RESULTS The patient demographics (e.g. age, body mass index), correct planned implant size and operative data were not significantly different between the two groups. The proportion of outliers in the coronal and sagittal plane ranged from 0% to 21% in both groups. Only the number of outliers for the posterior slope of the tibial component showed a significant difference (p = 0.004) with more outliers in the CT group (n = 9, 13%) than in the MRI group (0%). CONCLUSION The post-operative HKA-axis was comparable in the MRI- and CT-based PSGs, but there were significantly more outliers for the posterior slope in the CT-based PSGs. TAKE HOME MESSAGE Alignment with MRI-based PSG is at least as good as, if not better, than that of the CT-based PSG, and is the preferred imaging modality when performing TKA with use of PSG. Cite this article: Bone Joint J 2016;98-B:786-92.

Fast track and outpatient surgery in total knee arthroplasty: beneficial for patients, doctors and hospitals

Fast track programmes aim for optimising perioperative management using a multidisciplinary and individualised patient approach [5, 6]. A FT programme optimises patient care and allows an earlier discharge from hospital [5]. Outpatient surgical pathways even go one step further and aim for same day admission and discharge of the patient undergoing partial or even total knee arthroplasty [1, 2]. Over the last 15 years, FT programmes have proven beneficial for the patient, the knee surgeon as well as the health insurance system. Reduced length of stay and decreased morbidity comes along with similar rates of readmission or adverse events [5]. In fact, the length of hospital stay for knee arthroplasty patients has significantly decreased through the last decade, but still varies widely between hospitals and countries. However, in most of the hospitals a length of stay for UKA between 1 and 5 days and for TKA between 2 and 6 days is already reality. The length of hospital stay depends on a variety of different factors such as patient characteristics, comorbidities, hospital environment, the doctors will to work in a multidisciplinary approach and finally the health care reimbursement system [5]. Clearly, the reimbursement system is * Michael T. Hirschmann michael.hirschmann@ksbl.ch; michael.hirschmann@unibas.ch; Michael_Hirschmann@web.de http://www.kneedoctor.ch

Results of Cemented Anatomically Adapted Total Hip Arthroplasty: A Follow-Up Longer Than 10 years.

This retrospective single-center study evaluated the >10-year follow-up (FU) and survival of 2 anatomically adapted cemented total hip arthroplasties (THAs) in a series of 308 patients (323 THAs) with a mean age of 76.2 years at operation. At a mean of 11 years of FU, patient-reported outcome measures, clinical examination, and plain radiography were analyzed. In 6 THAs, the femoral and/or acetabular component was revised. Reasons for revision were aseptic loosening and infection. At >10 years of FU, there was an overall survival for both THAs of 98.1%. Radiographic radiolucent lines were seen in 15 THAs affecting Gruen zone 4 and Delee and Charnley zone II. We conclude that both anatomically adapted cemented THAs have an excellent survival at 11 years of FU.