CT-based patient-specific instrumentation for total knee arthroplasty in over 700 cases: single-use instruments are as accurate as standard instruments.

PURPOSE: Efforts in total knee arthroplasty are made to improve accuracy for a correct leg axis and reduce component malpositioning using patient-specific instruments. It was hypothesized that use of patient-specific instruments (vs. computer-navigated and conventional techniques) will reduce the number of outliers. Our second hypothesis was that single-use instrumentation will lead to the same accuracy compared to patient-specific instruments made of metal. METHODS: 708 primary total knee arthroplasties between 2014 and 2018 using computer tomography (CT)-based patient-specific cutting block technique and a preoperative planning protocol were retrospectively reviewed. Preoperative data [hip-knee-angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA), tibial slope, femoral component flexion] was compared to postoperative performed standard radiological follow-up X-rays. Differences of > 3° between measurements were defined as outliers. RESULTS: Overall 500 prostheses using standard instrumentation and 208 prostheses using single-use instruments were implanted. Preoperative HKA axes (- 1.2°; p < 0.001), femoral component flexion (Δ 0.8°, p < 0.001), LDFA (Δ - 1.5°, p < 0.001), MPTA (Δ - 0.5°, p < 0.001) and tibial posterior slopes (Δ 0.5°, p < 0.001), respectively, were different from postoperative axes. More outliers occurred using standard (vs. single-use) instruments (p < 0.001) regarding postoperative HKA (ranges of standard- vs. single-use: instruments: HKA 178.0°-180.5° vs. 178.0°-180.5°, femoral component flexion 0.0°-6.0° vs. 0.0°-4.5°, LDFA 90.0°-91.0° vs. 90.0°-90.0°, MPTA 90.0°-90.0° vs. 90.0°-90.0°, tibial posterior slope - 10° to 10° vs. - 1° to 10°). No differences were seen for other angles measured. Comparing both systems, total number of outliers was higher using standard (8%) vs. single-use instruments (4.3%). CONCLUSION: This study shows a high accuracy of CT-based patient-specific instrumentation concerning postoperative achieved knee angles and mechanical leg axes. Single-use instruments showed a similar accuracy. LEVEL OF EVIDENCE: III.

A novel augmented reality-based surgical guidance system for total knee arthroplasty.

INTRODUCTION: Many of the functional complications that arise after total knee arthroplasty (TKA) are caused by a non-optimal balance of the knee after surgery. Over the past 20 years, technology has been used in the Operating Room (OR) to help improve precision and balance. The results of Computer-Assisted Surgery (CAS) and robotic systems show improved accuracy regarding implant positioning but a relatively small improvement in patient-reported outcomes and implant survival compared to conventional TKA. Recently, Augmented Reality (AR) has been proposed as a technology that could improve accuracy in orthopaedic surgery, providing a more efficient and cost-effective solution. MATERIALS AND METHODS: This article describes a novel AR-based surgical guidance system that measures intra-operatively the effect of prosthesis alignment and positioning on soft tissue balance. The system is integrated in a pair of smart glasses and two small sensors and displays surgical targets directly in the field of view of the surgeon. RESULTS: The system has been used in a limited number of cases. While the preliminary experience has been positive, clinical research is ongoing to confirm to confirm the performance of the system and the impact on clinical outcomes. CONCLUSION: Augmented Reality can be a valuable tool to improve accuracy in TKA. The use of smart glasses and integrated sensors improves the efficiency of the procedure, particularly when coupled with single-use instrumentation. A novel protocol for soft tissue assessment allows for a 3-dimensional evaluation of the ligaments and a better measurement of the effect of tibial rotation.

Bone autografting in medial open wedge high tibial osteotomy results in improved osseous gap healing on computed tomography, but no functional advantage: a prospective, randomised, controlled trial.

PURPOSE: Medial open wedge high tibial osteotomy (owHTO) is a valuable surgical technique used to manage medial degeneration in varus knees. Iliac crest autograft is considered the gold standard gap-filler. It was hypothesised that iliac crest autograft promotes gap healing and improves functional outcome in owHTO. METHODS: Between 2005 and 2009, patients scheduled to undergo owHTO stabilised by a medial locking compression plate were randomised to undergo owHTO either with iliac crest autograft (group A) or without bone void filler (group B). Pre- and postoperative leg axes were recorded. At 3 and 12 months postoperatively, the healing of the osteotomy gap was measured as a percentage on CT images, and functional scores were recorded. RESULTS: There were 15 patients in group A, and 25 in group B. The groups were similar in age, sex ratio, knee varus deformity, body mass index, and smoking status. Group A and B had similar preoperative varus (6.9° vs. 7.6°) and postoperative valgus (2.2° vs. 3.0°). Compared with the control group, group A had a significantly greater degree of osseous gap healing after 3 months (40.1% vs. 10.8%, p = 0.045) and 12 months (91.5% vs. 59.1%, p ≤ 0.001). Multiple linear regression analysis found that bone grafting was an independent promoting factor for gap healing, while increased preoperative varus was an independent retardant factor at 3 months (p = 0.004 and p = 0.002, respectively) and 12 months (p ≤ 0.001 and p = 0.003, respectively). Younger age was a promoting factor for gap healing on CT at 3 months (p ≤ 0.001), but not at 12 months. No correlations were found between bone healing and functional outcome, body mass index, or smoking status. CONCLUSIONS: Iliac crest autograft significantly increases healing of the osteotomy gap after owHTO. Increased preoperative varus and older patient age are independent factors that delay early healing of the osteotomy. However, no functional advantage was found at 3 or 12 months postoperatively. Therefore, routine use of iliac crest autograft cannot be recommended. LEVEL OF EVIDENCE: II.

Prevalence and quantification of contamination of knitted cotton outer gloves during hip and knee arthroplasty surgery.

INTRODUCTION: Knitted cotton outer gloves offer protection against surgical glove perforation and provide improved grip on instruments. These gloves absorb blood and other fluids during surgery, and may therefore also accumulate contaminating bacteria. To date, there is no published data on microbial contamination of such gloves during surgery. METHODS: Knitted cotton outer gloves used in primary and revision hip and knee arthroplasty from two Swiss hospitals were analysed by quantitative bacteriology. Samples were subjected to sonication and vortexing, followed by membrane filtration of the sonicate. Membranes were incubated under aerobic and anaerobic culture conditions, respectively, for 21 days. Total microbial load for each pair of gloves was determined by colony-forming units (CFU) count. Strain identification was performed with MALDI-TOF. RESULTS: A total of 43 pairs of gloves were collected from continuous series of surgeries. Under aerobic culture conditions, total CFU counts ranged 0-1103, 25 (58%) samples remaining sterile, and 4 (9%) yielding > 100 CFU. Under anaerobic culture conditions, total CFU counts ranged 0-3579, 22 (51%) samples remaining sterile, 6 (14%) yielding > 100 CFU. The only covariate significantly associated with the level of contamination was the provider hospital (p < 0.0001 for aerobic and p = 0.007 for anaerobic cultures). Strain identification revealed only skin commensals, mainly coagulase-negative staphylococci and Propionibacterium spp. CONCLUSION: While contamination of surgical latex gloves is a well-known issue, no study has examined so far contamination of knitted cotton outer gloves. No or very low microbial contamination could be identified in the majority of the knitted cotton outer gloves assayed. However, a relevant proportion showed contamination far higher than estimated minimal thresholds for implant-associated infection. Clinical relevance of these findings remains to be established.

Complications after epiphyseal reconstruction of the anterior cruciate ligament in prepubescent children.

PURPOSE: Reconstruction of the anterior cruciate ligament (ACL) remains a major concern in the prepubescent, skeletally immature patient with wide open growth plates. Different surgical techniques have been proposed. This study reports the results and complications of ACL reconstruction in young children using an all epiphyseal technique. METHODS: Between 2006 and 2010, 12 patients (10-13 years, median 12.1 years) underwent epiphyseal primary ACL reconstruction, with a total of 13 knee procedures. Patients were assessed retrospectively with a median follow-up of 54 months (range 39-80 months) consisting of a clinical examination, instrumented arthrometer testing and radiological analysis. Functional status was assessed using the Lysholm knee score, Tegner activity scale and IKDC-2000 form. RESULTS: According to the IKDC examination form, five knees were rated as normal, six near normal and two abnormal. The median IKDC score at follow-up was 88.5 points (range 75-99 points). The mean side-to-side difference in KT-1000 ligament laxity testing was 1.5 mm (±2.5 mm). In two patients, reoperation was necessary due to graft failure. Two patients developed significant leg length inequality; one with 20 mm overgrowth and varus malalignment after re-reconstruction and the second developed arthrofibrosis and overgrowth of 16 mm. Four patients had minor limb length discrepancy ranging between +5 and +10 mm; no growth arrest was noted. One patient with an intact but slightly elongated graft required a meniscal suture 34 months after ACL reconstruction following a traumatic medial meniscal lesion. CONCLUSION: Despite using the epiphyseal technique in ACL reconstruction, relevant growth discrepancy can occur. Thereby, overgrowth rates appear to potentially pose a major clinical problem, which has remained unreported so far. Overall, there is a considerable high risk of complications in this patient group. LEVEL OF EVIDENCE: IV.

The tibial-tubercle trochlear groove distance in patients with trochlear dysplasia: the influence of the proximally flat trochlea.

PURPOSE: Increased tibial tubercle trochlear groove distance (TT-TG) is frequently associated with trochlear dysplasia (TD). Since the trochlear groove appears more distally in patients with TD compared to controls, it is unknown whether TT-TG might be comparable and meaningful. METHODS: Fifty patients with TD were retrospectively analysed and compared to 52 age- and gender-matched patients (CG). TT-TG was measured on transverse MR images, as the distance between the trochlear groove of minimal 2 mm depth proximally and the centre of the patellar tendon at its distal insertion. The height of the femoral reference point above joint line was recorded for both groups. TT-TG measurement was repeated in CG using the first (P25), second (P50) and third quartile (P75) above joint line of TD. RESULTS: Patients with TD had a significantly smaller vertical distance between the most proximal trochlear deepening and the femorotibial joint line (20.6 mm, range 10.3-30.9) compared to CG (33.8 mm, range 25.4-41.1; p < 0.001). TT-TG values measured at 20 mm (P50) and 15 mm (P25) proximal to the femorotibial joint line were significantly smaller compared when measured with the most proximal reference point [1.8 mm (95 % CI 1.3-2.3, p < 0.001) and 2.4 mm (95 % CI 1.9-3.0, p < 0.001)] in CG. The inter-rater reliability was excellent (ICC 0.99). CONCLUSION: TT-TG distance depends significantly on the femoral reference point. Since the trochlear groove is seen more distally in patients with TD compared to controls, TT-TG of the patients with highest risk of recurrent patellar instability might be underestimated. LEVEL OF EVIDENCE: Diagnostic study, Level I.

Evaluation of a virtual-reality-based simulator using passive haptic feedback for knee arthroscopy.

PURPOSE: The aim of this work is to determine face validity and construct validity of a new virtual-reality-based simulator for diagnostic and therapeutic knee arthroscopy. METHODS: The study tests a novel arthroscopic simulator based on passive haptics. Sixty-eight participants were grouped into novices, intermediates, and experts. All participants completed two exercises. In order to establish face validity, all participants filled out a questionnaire concerning different aspects of simulator realism, training capacity, and different statements using a seven-point Likert scale (range 1-7). Construct validity was tested by comparing various simulator metric values between novices and experts. RESULTS: Face validity could be established: overall realism was rated with a mean value of 5.5 points. Global training capacity scored a mean value of 5.9. Participants considered the simulator as useful for procedural training of diagnostic and therapeutic arthroscopy. In the foreign body removal exercise, experts were overall significantly faster in the whole procedure (6 min 24 s vs. 8 min 24 s, p < 0.001), took less time to complete the diagnostic tour (2 min 49 s vs. 3 min 32 s, p = 0.027), and had a shorter camera path length (186 vs. 246 cm, p = 0.006). CONCLUSION: The simulator achieved high scores in terms of realism. It was regarded as a useful training tool, which is also capable of differentiating between varying levels of arthroscopic experience. Nevertheless, further improvements of the simulator especially in the field of therapeutic arthroscopy are desirable. In general, the findings support that virtual-reality-based simulation using passive haptics has the potential to complement conventional training of knee arthroscopy skills. LEVEL OF EVIDENCE: II.

Assessment of lower limb length and alignment by biplanar linear radiography: comparison with supine CT and upright full-length radiography.

OBJECTIVE: The purpose of this article is to compare lower limb length and alignment measurements on supine CT, upright full-length radiography, and 3D models based on upright biplanar linear radiography. SUBJECTS AND METHODS: This study involved 51 consecutive patients (22 men and 29 women; mean age, 68.8 years; range, 43-92 years) who were scheduled for total knee replacement. Lower limb length and alignment angle were measured on CT, upright full-length radiography, and 3D models based on biplanar linear radiography with standard and composed leg methods by two independent readers. Descriptive statistics of each modality were calculated. Measurements of different modalities were compared by paired Student t tests. Agreement between readers and modalities was assessed by Bland-Altman analyses. RESULTS: Mean (± SD) limb lengths were 783 ± 56.1 mm (range, 639-927 mm), 785 ± 53.0 mm (range, 655-924 mm), 780 ± 55.4 mm (range, 633-921 mm), and 783 ± 55.9 mm (range, 636-924 mm) for CT, upright full-length radiography, and 3D models based on biplanar linear radiography standard and composed leg measurements, respectively. Mean alignment angles were 2.3° ± 5.5° (range, -12° to 20°) for CT, 2.5° ± 6.7° (range, -17° to 18°) for upright full-length radiography, and 3.4° ± 6.6° (range, -14° to 18°) for 3D models based on biplanar linear radiography. No significant differences among modalities for mean limb length were found when using composed leg measurements in biplanar linear radiography. Very small but significant mean differences in angle measurements were seen for CT (-1.1° ± 2.5) and upright full-length radiography (-0.9° ± 3.1) compared with biplanar linear radiography. Bland-Altman analyses showed no significant differences between readers, with the highest agreement for biplanar linear radiography length measurements. CONCLUSION: Measurements on 3D models based on upright biplanar linear radiographs allow lower limb length and alignment angle measurements that are interchangeable with supine CT scans and upright full-length radiographs but with superior interreader agreement.

End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers.

PURPOSE: Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images. METHODS: Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3 mm, matrix: 256 × 384, FOV: 150 × 150 mm. Two observers independently measured the TTTG at all positions. RESULTS: Mean TTTG for observer 1 was 15.1 ± 3.2 mm at full extension, 10.0 ± 3.5 mm at 15° flexion and 8.1 ± 3.4 mm at 30° flexion. Mean TTTG for observer 2: 14.8 ± 3.3 mm at full extension, 9.4 ± 3.0 mm at 15° flexion, 8.6 ± 3.4 mm at 30° flexion. Mean values were significantly different (p < 0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p < 0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87-0.88; p < 0.001). CONCLUSIONS: The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited.

Biomechanical Comparison of Anterior Cruciate Ligament Reconstruction Using a Single-Bundle Round or Ribbon-like Hamstring Tendon Graft.

BACKGROUND: Persistent instability of the knee is reported in up to 30% of patients after anterior cruciate ligament (ACL) reconstruction. Based on anatomic findings showing that ACL is a flat ribbon-like structure that twists during knee flexion, a new surgical ACL reconstruction technique using a ribbon-like graft has been developed. However the effect of this surgical technique on knee kinematics has not yet been evaluated. PURPOSE: To compare the anteroposterior and rotational stability of the knee after ACL reconstruction using single-bundle (SB) round and ribbon-like grafts in anterolateral-intact/deficient knees. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve human fresh-frozen cadaveric knees were tested with a 6 degrees of freedom robotic system. Internal rotation and anterior translation of the knee were recorded from 0° to 90° of flexion. A full kinematic assessment was performed in each of the following conditions: (1) intact knee, (2) after sectioning of the ACL, (3) after ACL reconstruction using a SB hamstring tendon graft in a round configuration and a ribbon-like configuration, and (4) after sectioning of the anterolateral structures. One-way analysis of variance and post hoc Tukey tests were used for statistical analyses. RESULTS: When compared with the intact knee, the ACL-deficient knee demonstrated a mean ± SD increase in anterior translation and internal rotation of 6.3 ± 2.5 mm (P < .01) and 5.8°± 2.3° (P < .01), respectively. After ACL reconstruction using a SB ribbon-like graft, the mean difference in anterior translation and internal rotation as compared with the intact knee was -0.1 ± 1.5 mm (P = .842) and 0.0°± 1.1° (P = .999). These differences from the intact knee were also not significant after ACL reconstruction using a round graft (-0.1 ± 1.3 mm, P = .999; -0.5°± 1.5°, P = .401). In the ACL-reconstructed knee using either a ribbon-like or round graft, sectioning of the anterolateral structures did not induce a significant increase of anterior translation and internal rotation of the knee. CONCLUSION: ACL reconstruction using a SB ribbon-like or round graft restored the kinematics of the intact knee at time zero. Secondary sectioning of the anterolateral structures in the ACL-reconstructed knee using both types of graft did not significantly affect the anterior translation and internal rotation of the knee. CLINICAL RELEVANCE: This is the first biomechanical study on the new ACL reconstruction technique using a ribbon-like graft.

Femoral and tibial torsion measurements with 3D models based on low-dose biplanar radiographs in comparison with standard CT measurements.

OBJECTIVE: The purpose of this study was to evaluate the interchangeability of femoral and tibial torsion measurements obtained with 3D models based on low-dose biplanar radiographs and standard CT measurements by testing the following two hypotheses: that there is excellent agreement between the two methods and that there is excellent interreader agreement. MATERIALS AND METHODS: Two independent readers used 3D models based on low-dose simultaneous biplanar radiographs and axial CT images to measure femoral and tibial torsion in 35 patients (mean age, 65 years; range, 46-89 years) with osteoarthritis of the knee who were to undergo prosthesis insertion. The two measurements were compared by means of Bland-Altman plots and descriptive statistics. Interreader agreement was quantified with intraclass correlation coefficients. RESULTS: The average differences between readers on the CT measurements were 1.3° (range, 0°-11°) for the femur and 1.5° (range, 0°-12°) for the tibia. The average differences for the measurements obtained with the 3D model were 0.1° (range, 0°-9°) for the femur and 0.8° (range, 0°-10°) for the tibia. The average differences between the two methods were 0° (range, -5° to 7°) for the femoral measurements and 3° (range, -12° to 5°) for the tibial measurements. Bland-Altman plots showed no relevant differences between the results of the two measurement modalities. Except for one measurement of femoral torsion and one measurement of tibial torsion, all results based on the 3D models were within the 95% limit of agreement (mean ± 1.96 SD). Interreader agreement was statistically significant (p < 0.001) for all measurements with high intraclass correlation coefficients (> 0.9). CONCLUSION: Femoral and tibial torsion measurements obtained with 3D models based on biplanar radiographs are interchangeable with standard CT measurements in patients with osteoarthritis of the knee.

Haemophilic knee arthropathy: long-term outcome after total knee replacement.

PURPOSE: The objective of this study was to evaluate the long-term outcome and prosthetic survival of primary total knee arthroplasty in haemophilic patients. It was hypothesized that the infection and revision rate are higher and the outcome inferior when compared with patients without haemophilia. METHODS: Between 1985 and 2004, forty-three consecutive primary total knee replacements were performed in thirty haemophilic patients. These patients' charts were reviewed retrospectively. Twenty-five patients (34 knees) were available for clinical and radiological follow-up. The outcome was assessed using the Knee Society score, WOMAC and Kaplan-Meier survivorship analysis. RESULTS: An haematogenous infection occurred in two patients. In three patients, component revision was needed: two because of an infection and one because of a mechanical failure. After a mean follow-up of 9.6 years (2-20), 94% of the patients rated their result as either excellent or good. At time of follow-up, the Knee Society Score averaged 73.3 points (range, 29-100) and showed a significant gain (p < 0.001) compared to preoperative. Flexion contracture could be reduced significantly (p < 0.001) from 18.1° preoperatively to 8.4° at follow-up, whereas flexion remained unchanged. When infection or any component replacement was set as endpoints, the 10 years prosthetic survival was 90 and 86%, respectively. CONCLUSION: Total knee arthroplasty in haemophilic patients is a reliable treatment that results in pain relief and functional improvement with a low risk of postoperative infection. However, neither the postoperative infection rate nor the functional result does reach the same level as in a population not affected by haemophilia. LEVEL OF EVIDENCE: IV.

Embossing of a screw thread and TCP granules enhances the fixation strength of compressed ACL grafts with interference screws.

PURPOSE: Fixation of soft tissue grafts with interference screws relies on the friction of the graft between the screw and the bone tunnel. The goal of this study was to precondition such grafts by mechanical compression in order to reduce anticipated and undesired viscoelastic adaptation of the graft to screw pressure. Further, the otherwise slippery graft surface was modified with impressed tricalcium phosphate granules (TCP) to improve friction and mechanical hold. METHODS: Fresh flexor digitorum tendons from young bovines were used to create bundles with a diameter of 8-9 mm and were divided into 10 groups to compare the pullout strength and bone damage in a variety of construct scenarios. Specifically, the effects of graft precompression to reduce preimplantation graft diameter were investigated. Further the effects of impressing TCP granules and/or a screw thread into the tendon surface during the compression process were studied. RESULTS: In sawbone tests, radial graft compression allowed for a smaller bone tunnel (7 mm), but resulted in a significantly lower pullout strength of 174 N (95% CI: 97, 250), compared with controls [315 N (204, 426)]. In contrast, TCP coated [402 N (243, 561)], screw embossed grafts [458 N (302, 614)], and the combination of TCP and embossing [409 N (274, 543)] achieved higher pullout strengths when compared to the standard technique. In porcine bone, untreated grafts using an 8 mm screw pulled out at 694 ± 93 N, significantly higher loads were required to pullout compressed grafts with or without TCP coating (870 ± 74 and 878 ± 131 N), yet fixed with a 7 mm screw. CONCLUSION: Modification of the tendon graft surface has a large influence on the biomechanical performance of interference screw fixation and results in less bone damage inflicted during insertion to a smaller tunnel diameter, while simultaneously achieving superior pullout strength.

ISB clinical biomechanics award winner 2021: Tibio-femoral kinematics of natural versus replaced knees - A comparison using dynamic videofluoroscopy.

BACKGROUND: A comparison of natural versus replaced tibio-femoral kinematics in vivo during challenging activities of daily living can help provide a detailed understanding of the mechanisms leading to unsatisfactory results and lay the foundations for personalised implant selection and surgical implantation, but also enhance further development of implant designs towards restoring physiological knee function. The aim of this study was to directly compare in vivo tibio-femoral kinematics in natural versus replaced knees throughout complete cycles of different gait activities using dynamic videofluoroscopy. METHODS: Twenty-seven healthy and 30 total knee replacement subjects (GMK Sphere, GMK PS, GMK UC) were assessed during multiple complete gait cycles of level walking, downhill walking, and stair descent using dynamic videofluoroscopy. Following 2D/3D registration, tibio-femoral rotations, condylar antero-posterior translations, and the location of the centre of rotation were compared. FINDINGS: The total knee replacement groups predominantly experienced reduced tibial internal/external rotation and altered medial and lateral condylar antero-posterior translations compared to natural knees. An average medial centre of rotation was found for the natural and GMK sphere groups in all three activities, whereas the GMK PS and UC groups experienced a more central to lateral centre of rotation. INTERPRETATION: Each total knee replacement design exhibited characteristic motion patterns, with the GMK Sphere most closely replicating the medial centre of rotation found for natural knees. Despite substantial similarities between the subject groups, none of the implant geometries was able to replicate all aspects of natural tibio-femoral kinematics, indicating that different implant geometries might best address individual functional needs.

Comparative Cost Analysis of Four Different Computer-Assisted Technologies to Implant a Total Knee Arthroplasty over Conventional Instrumentation.

Several computer-assisted technologies, such as navigation and robotics, have been introduced to Total Knee Arthroplasty (TKA) in order to increase surgical precision and reduce complications. However, these technologies are often criticized due to the increased costs and effort associated with them; however, comparative data are missing. The aim of the present study was to evaluate differences in intraoperative workflows and the related perioperative cost-profiles of four current computer-assisted technologies, used to implant a TKA, in order to gain a comparison to conventional instrumentation. For the cost analysis, additional preoperative imaging and instruments, increased operating room (OR) and planning-time, and expenditures for technical support of the equipment and disposals were calculated, in comparison to conventional TKA, for (1) standard computer-navigation, (2) patient specific instruments (PSI), (3) image-based robotic assistance, and (4) imageless robotic assistance. Workflows at four expert centers which use these technologies were reviewed by an independent observer. The total cost calculation was based on a 125 TKA per year unit in Switzerland. Computer-navigation resulted in 14 min (+23%) increased surgery time and, overall, USD 650 in additional costs. PSI technology saved 5 min (8%) OR time but it created USD 1520 in expenditures for imaging and disposals. The image-based robotic system was the most expensive technology; it created overall additional costs of USD 2600, which predominately resulted from technical support, disposals, the CT-Scan, and 14 min of increased OR time. The imageless robotic assistance resulted in the largest increase in OR-time, as it resulted in an additional 25 min (+42%) on average. Overall, additional costs of USD 1530 were calculated. Every one of the assistive technologies in this study increased the total cost of TKA when compared to a conventional technique, and the most important variables, related to cost, were technical support and additional disposables. The longer surgical times and additional surgical trays required for the techniques had a marginal effect on overall costs. This comparative cost analysis gives valuable information for future efforts to calculate the real costs of these technologies and the subsequent return on investment of each technique.

Classification of trochlear dysplasia as predictor of clinical outcome after trochleoplasty.

PURPOSE: Sulcus-deepening trochleoplasty restores the trochlear groove in patients with patellofemoral instability and underlying trochlear dysplasia. There are types of dysplasia both with (B and D) and without (A and C) a supratrochlear spur. The aim of this study was to identify influencing factors for the clinical outcome following trochleoplasty. METHODS: Forty-four knees in 38 patients who underwent trochleoplasty for instability (type A in 9, B in 15, C in 9 and D in 11 knees) were assessed clinically with the Kujala score and radiologically with radiographs and MRI. The median follow-up was 4 (2-7.8) years. RESULTS: At follow-up, the median Kujala score had improved from 68 (29-84) to 90 (42-100) points (P < 0.001). Instability (P < 0.001) and pain (P = 0.027) decreased significantly, but in 3 knees, pain was worse postoperatively. Twenty-seven knees were ranked as excellent, 10 as good, 2 as fair and 5 as poor. Overall, dysplasia types B and D benefited more from surgery than types A and C. The postoperative MRI revealed no chondrolysis or subchondral necrosis, but deterioration of cartilage on the lateral trochlear facet was identified. CONCLUSION: Trochleoplasty is a useful and reliable surgical technique to improve patellofemoral instability in patients with a dysplastic trochlea. While improved stability is predictable, pain is less predictable and may even increase following surgery. The overall results were directly dependent on the type of the dysplasia, with a significantly better clinical outcome in type B and D. The clinical relevance of this study is that severe dysplasia can successfully be treated with trochleoplasty. LEVEL OF EVIDENCE: III.

Epicondylar advancement osteotomy for flexion gap asymmetry after total knee replacement.

A possible cause for a painful total knee prosthesis is flexion gap asymmetry with medial or lateral instability despite adequate axial and rotational alignment of both components and adequate extension gap balancing. To avoid component exchange, ligament advancement techniques can be used. Soft tissue procedures carry the risk of insufficiently stable scarring. Epicondylar sliding osteotomies are accepted as a mode of collateral ligament release in severe varus or valgus knee arthroplasties. We describe a technique of anterior epicondylar advancement for the correction of symptomatic flexion gap instability.

Closing wedge patellar osteotomy in combination with trochleoplasty.

Sulcus-deepening trochleoplasty may result in a serious patellofemoral incongruence in cases where the patella also is highly dysplastic. In such cases, a closing wedge osteotomy of the patella may be considered. The technique was used in two patients (both female, 16 1/2 and 14 years old respectively) out of 85 trochleoplasties performed. At two years follow-up, both patients showed a stable patella with correct tracking. Both considered their functional result as excellent. Postoperative radiographs showed a normal sulcus angle (135 degrees and 132 degrees) with good congruence. Closing wedge patellar osteotomy, combined with sulcus-deepening trochleoplasty, can increase patellofemoral congruence with good clinical outcome.

Novel measurement technique of the tibial slope on conventional MRI.

UNLABELLED: The posterior inclination of the tibial plateau, which is referred to as posterior tibial slope, is determined routinely on lateral radiographs. However, radiographically, it is not always possible to reliably recognize the lateral plateau, making a separate assessment of the medial and lateral plateaus difficult. We propose a technique to measure the plateaus separately by defining a tibial longitudinal axis on a conventional MRI. The medial plateau posterior tibial slope obtained from radiographs was compared with MR images in 100 consecutive patients with knee pain when ligament or meniscal injury was assumed. The posterior tibial slope on MRI correlated with those on radiographs. The mean posterior tibial slope was 3.4 degrees smaller on MRI compared with radiographs (4.8 degrees +/- 2.4 degrees versus 8.2 degrees +/- 2.8 degrees , respectively). The reproducibility was slightly better on radiographs than MRI (+/- 0.9 degrees versus +/- 1.4 degrees ). Twenty-one of the 100 cases had more than a 5 degrees difference (range, -8.7 degrees to 8.9 degrees ) between the medial and lateral plateaus. The proposed technique allows measurement of the posterior tibial slope of the medial and lateral plateaus on a standard knee MRI. By using this novel measurement technique, a reliable assessment of the medial and lateral tibial plateaus is possible. LEVEL OF EVIDENCE: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.