Measurement of knee joint motion using digital imaging

Usefulness of digital measurements for functional evaluation of paediatric elbow range of motion

BACKGROUND

Elbow immobilization due to fractures of the upper limb is frequent in paediatric patients. Proper follow-up is critical to assess elbow functional recovery. Telemedicine can be an option for remote monitoring of these patients. The purpose of this study was to compare personal and virtual evaluation of elbow range of motion after long arm cast withdrawal in paediatric patients.

METHODS

An observational cross-sectional study was carried out which included all paediatric patients with elbow immobilization in long arm casts treated at our centre. After cast withdrawal, elbow range of motion was evaluated by telemedicine and in office consultation in all four movements (flexion, extension, pronation and supination).

RESULTS

Ninety-three patients met the selection criteria. Median age at time of immobilization was 8 years. Mean elbow immobilization time was 23 days (range 18-56 days). When comparing office and remote measurements, no statistical differences were found for any of the four elbow movements measured in our study.

CONCLUSIONS

Remote evaluation of elbow range of motion by telemedicine is technically feasible. We evaluated elbow range of motion in paediatric patients after immobilization and we did not find differences between digital and in office measurements. The results were similar to those obtained through assessment in the office. We believe that this is a useful tool to facilitate remote patient follow-up.

Development of a Manual Measurement Device for Measuring Hallux Valgus Angle in Patients with Hallux Valgus

Background: Hallux valgus (HV) is one of the most common forefoot deformities, and its prevalence increases with age. HV has been associated with poor foot function, difficulty in fitting footwear and poor health-related quality of life. The aims of this study were to design and develop an easy-to-use measurement device for measuring hallux valgus angle (HVA) in patients with HV and to assess the measurement reliability of the newly designed measurement device. Methods: A manual measurement device for measuring HVA was designed and developed to test on patients with HV. Two measuring methods, i.e., test–retest and intra-observer measurements, were used to evaluate the repeatability and reliability of the newly designed measurement device. In the test–retest measurements, a total of 42 feet from 26 patients with HV were repeatedly measured by the same researcher using the manual measurement device every 3 weeks over a period of 12 months. The measurement reliability of the newly designed measurement device was analysed based on the collected HVA data. In the intra-observer measurements, a total of 22 feet from the same group of HV patients were measured by the same researcher using the manual measurement device and by a consultant using X-ray measurement for comparison. The intraclass correlation coefficient (ICC) was used to determine the correlation of measurements between the manual measurement device and X-ray measurement. Results: The mean of the difference between the two repeat measurements of HVA using the newly designed manual device was 0.62°, and the average of ICC was 0.995, which indicates excellent reliability. The ICC between X-ray and the average of twice-repeated manual measurements was 0.868, with 95% CI (0.649, 0.947) (p = 0.000). When the relationship in HVA between X-ray measurement and manual measurement using the new device was regressed as a linear relationship, the regression equation was y = 1.13x − 4.76 (R² = 0.70). Conclusions: The newly designed measurement device is easy to use, with low-cost and excellent reliability for HVA measurement, with the potential for use in clinical practice.

The "Wind Surf" Deformity-Correcting Fixed Flexion Deformity and Hyperextension in Bilateral CAS TKA

Severe knee arthritis can result in complex coronal and sagittal angular deformities. Windswept deformity is used to describe a varus deformity and contralateral valgus deformity. We recognized a new sagittal pattern at the time of computer-assisted surgery (CAS) in total knee arthroplasty (TKA) in which one knee has a fixed flexion deformity (FFD), while the contralateral knee has a hyperextension deformity. We propose to define it as "wind surf" deformity mimicking the opposite pull of the wind and a surfer. The incidence of "wind surf" deformity in this series was 0.96% among a cohort of 2,291 bilateral TKAs performed between 2013 and 2018. Twenty-two patients were identified with an FFD of 5° to 20° on one knee and recurvatum of -5° to -20° on the contralateral knee. Additional bone resection and soft-tissue releases were performed for the FFD with a goal to maintain residual 1° to 3° of flexion. Minimal bone resection and soft-tissue disruption were performed on the knee with hyperextension with a goal to maintain 5° to 7° of flexion. These opposite strategies applied with the help of CAS prevented recurrence resulting in satisfactory clinical results at 2-year follow-up. The "wind surf" deformity variant should be identified in patients presenting with severe knee arthritis to guide surgical treatment, prevent recurrence, and obtain favorable clinical patient outcomes.

Measurement of finger joint motion after flexor tendon repair: smartphone photography compared with traditional goniometry

The purpose of our study was to determine whether smartphone photography is as reliable and valid as clinical goniometry for measuring interphalangeal joint range of motion. We conducted a retrospective review of 37 fingers in 33 patients after flexor tendon repair. The measurements on photographs taken with a smartphone by a surgeon were compared with manual measurements with goniometry by the same surgeon. Pearson coefficients and interclass correlation coefficients were all above 0.85, and Bland-Altman analysis demonstrated that at least 35 of 37 measurements were within the 95% confidence interval in all variables. According to the Tang criteria, the total number of excellent and good results were equivalent according to both methods. There was high interobserver reliability between measurements by surgeons and a therapist. We conclude that if the pictures are properly taken, the measurement of the angles in the smartphone pictures are as reliable as measuring the angles with goniometry and that grading of the results according to the two methods gives identical results.

Accuracy of Measuring Knee Flexion after TKA through Wearable IMU Sensors

Wearable sensors have the potential to facilitate remote monitoring for patients recovering from knee replacement surgery. Using IMU sensors attached to the patients' leg, knee flexion can be monitored while the patients are recovering in their home environment. Ideally, these flexion angle measurements will have an accuracy and repeatability at least on par with current clinical standards. To validate the clinical accuracy of a two-sensor IMU system, knee flexion angles were measured in eight subjects post-TKA and compared with other in-clinic angle measurement techniques. These sensors are aligned to the patients' anatomy by taking a pose resting their operated leg on a box; an initial goniometer measurement defines the patients' knee flexion while taking that pose. The repeatability and accuracy of the system was subsequently evaluated by comparing knee flexion angles against goniometer readings and markerless optical motion capture data. The alignment pose was repeatable with a mean absolute error of 1.6 degrees. The sensor accuracy through the range of motion had a mean absolute error of 2.6 degrees. In conclusion, the presented sensor system facilitates a repeatable and accurate measurement of the knee flexion, holding the potential for effective remote monitoring of patients recovering from knee replacement surgery.

Effects of moving cupping therapy on hip and knee range of movement and knee flexion power: a preliminary investigation

Cupping therapy has become more popular in the sports setting because of its simplicity in application, minimal adverse effects, and reduction in pain and muscle tenderness, yet there is little research on its effectiveness for range of movement and power.Objectives: The primary aim of this study was to investigate if a single session of moving cupping to the posterior aspect of the lower limb effects hip and knee range of movement and knee flexion power. The secondary aim was to consider participants' views and perceptions of moving cupping therapy.Methods: Twenty-one healthy participants (12 male and 9 female) aged between 19 and 31 years volunteered to take part in the study. All participants received 15 min of moving cupping therapy to their dominant posterior lower extremity. Hip and knee range of movement and knee flexion isokinetic power measurements were taken prior to and immediately after the moving cupping intervention. Participants also completed a questionnaire based on their experience and perceptions of cupping.Results: Results showed a significant increase (p = <.05) in hip and knee range of movement measurements by 7% in the straight leg raise and 4% in a popliteal angle test. However, no significant changes were seen in the knee flexion power measures. Data from the questionnaire suggest that despite moving cupping being reported as 'uncomfortable' it is considered acceptable.Discussion: Moving cupping therapy may have short-term changes to range of movement but not power, though the limitations of this study mean that rigorous studies are required before the effectiveness of moving cupping can be determined.

Can stretch sensors measure knee range of motion in healthy adults?

Study aim: There are currently limited methods available to access dynamic knee range of motion (ROM) during free-living activities. This type of method would be valuable for monitoring and progressing knee rehabilitation. Therefore, the aim of this study was to evaluate the functioning of stretch sensors for the measurement of knee ROM and to assess the level of the measurement error. Material and methods: Nine healthy participants were included in the study. Three stretch sensors (StretchSense™, Auckland, NZ) were attached on the participants’ right knees by Kinesiotape®. A Cybex dynamometer was used to standardise movement speed of the knee joint. Data was recorded through the StretchSense™ BLE application. Knee angles were obtained from the video clips recorded during the testing and were analysed by MaxTraq® 2D motion analysis software. The knee angles were then synchronised with the sensor capacitance through R programme. Results: Seven out of the nine participants presented with high coefficient of determination (R2) (>0.98) and low root mean square error (RMSE) (<5°) between the sensor capacitance and knee angle. Two participants did not confirm good relationship between capacitance and knee angle as they presented high RMSE (>5°). The equations generated from these 7 participants’ data were used individually to predict knee angles. Conclusions: The stretch sensors can be used to measure knee ROM in healthy adults during a passive, non-weight-bearing movement with a clinically acceptable level of error. Further research is needed to establish the validity and reliability of the methodology under different conditions before considered within a clinical setting.

Noninvasive navigated assessment of the lower limb axis prior to knee arthroplasty: a feasibility study

The purpose of the study was to assess accuracy and repeatability of a noninvasive navigated (NIN) measurement of the lower limb axes by comparison with the conventional, invasive navigated (IN) technique. The tested hypothesis was that NIN measure will significantly differ from IN measure when performed on a supine patient under general anesthesia just prior to knee arthroplasty. The accuracy study involved 20 cases. The following measures were performed with both systems: maximal extension angle, coronal mechanical femoro-tibial angle at the previously assessed maximal extension angle, coronal mechanical femoro-tibial angle at 30° of knee flexion. NIN and IN measures were compared with the appropriate statistical tests. The repeatability study involved 14 cases. The same measures were performed with the NIN system twice by two independent observers. The intra- and inter-observer variability was assessed by the calculation of the intra-class correlation coefficient. After correction for the systematic biases, the differences between the two systems were not significant. A good correlation, a good coherence and an excellent agreement between NIN and IN measures of maximal extension angle and coronal femoro-tibial mechanical angle at maximal extension. But measures at 30° of flexion were inconsistent. The NIN system can be considered as an accurate and precise tool for the assessment of the knee extension angle and the coronal deformation at maximal extension prior to knee arthroplasty. But this system is less accurate and less repeatable when measuring coronal femoro-tibial mechanical angle at 30° of flexion and should not be used for this purpose.

Inter-rater reliability and validity of angle measurements using smartphone applications for weight-bearing ankle dorsiflexion range of motion measurements

OBJECTIVES

The purpose of this study was to examine the inter-rater reliability, validity, and error of angle measurements for ankle dorsiflexion range of motion while in the weight-bearing position using a smartphone application.

DESIGN

Reliability and validity study.

SETTING

Measurement positions were performed by one experienced examiner.

PARTICIPANTS

Eighteen volunteers participated in the study. Three examiners (examiner 1 and examiner 2 had completed the course to become qualified certified athletic trainers and examiner 3 did not belong to the course) performed smartphone application measurements.

MAIN OUTCOME MEASURES

Ankle dorsiflexion range of motion was measured in the lunge position. Radiographic measurements were performed using a bony landmark. The markerless method for application measurements was used, using a body part as a landmark.

RESULTS

Using the markerless method for application measurements, the intra-class correlation coefficients were 0.945. Using Pearson's correlation coefficient and intra-class correlation coefficients to compare the radiographic measurements and markerless method for application measurements, three examiners showed very high correlation (r > 0.9) and almost perfect (>0.81) intra-class correlation coefficient. Error values were less than 5° according to examiner 1 and examiner 2.

CONCLUSION

Smartphone application measurements using the markerless method of ankle dorsiflexion range of motion exhibited inter-rater reliability and high validity.

How Does Level and Type of Experience Affect Measurement of Joint Range of Motion?

OBJECTIVES

Comparison of range of motion measurements by 3 types of investigators with different levels and types of training using three different measurement techniques. The study hypothesis was that the accuracy and precision of range of motion measurements would vary based on (1) the level and type of experience of the investigator and (2) the measurement technique used.

DESIGN/SETTING

Descriptive laboratory study.

PARTICIPANTS

Ten fresh frozen cadavers (20 upper and 20 lower extremities).

INTERVENTIONS

Shoulder, elbow, hip, and knee motion were measured using 3 different measurement techniques (digital photography, goniometry, and visual estimation) by 3 groups of investigators (attending orthopedic surgeons, physical therapists, and residents). Accuracy was defined by the difference from the reference standard (motion capture analysis), whereas precision was defined by the proportion of measurements within either 5° or 10° of the reference standard. Analysis of variance, t-tests, and chi-squared tests were used.

RESULTS

Statistically significant (p < 0.05) differences in accuracy were found for hip flexion, abduction, internal rotation, external rotation, and knee flexion. However, none of these differences met the authors' defined clinical significance (maximum difference 3°). Precision was significantly (p < 0.05) different for elbow extension, hip flexion, abduction, internal rotation, external rotation, and knee flexion.

CONCLUSION

This study found that clinically accurate measurements of shoulder, elbow, hip, and knee motion are obtained regardless of technique used or the investigators' level and type of experience. Precision was equivalent for all shoulder motions, elbow flexion, and knee extension, but varied by as much as 7% to 28% between groups for all other motions.

Is digital photography an accurate and precise method for measuring range of motion of the shoulder and elbow?

BACKGROUND

Accurate measurements of shoulder and elbow motion are required for the management of musculoskeletal pathology. The purpose of this investigation was to compare three techniques for measuring motion. The authors hypothesized that digital photography would be equivalent in accuracy and show higher precision compared to the other two techniques.

METHODS

Using infrared motion capture analysis as the reference standard, shoulder flexion/abduction/internal rotation/external rotation and elbow flexion/extension were measured using visual estimation, goniometry, and digital photography on 10 fresh frozen cadavers. These measurements were performed by three physical therapists and three orthopaedic surgeons. Accuracy was defined by the difference from the reference standard (motion capture analysis), while precision was defined by the proportion of measurements within the authors' definition of clinical significance (10° for all motions except for elbow extension where 5° was used). Analysis of variance (ANOVA), t-tests, and chi-squared tests were used.

RESULTS

Although statistically significant differences were found in measurement accuracy between the three techniques, none of these differences met the authors' definition of clinical significance. Precision of the measurements was significantly higher for both digital photography (shoulder abduction [93% vs. 74%, p < 0.001], shoulder internal rotation [97% vs. 83%, p = 0.001], and elbow flexion [93% vs. 65%, p < 0.001]) and goniometry (shoulder abduction [92% vs. 74%, p < 0.001] and shoulder internal rotation [94% vs. 83%, p = 0.008]) than visual estimation. Digital photography was more precise than goniometry for measurements of elbow flexion only [93% vs. 76%, p < 0.001].

CONCLUSIONS

There was no clinically significant difference in measurement accuracy between the three techniques for shoulder and elbow motion. Digital photography showed higher measurement precision compared to visual estimation for shoulder abduction, shoulder internal rotation, and elbow flexion. However, digital photography was only more precise than goniometry for measurements of elbow flexion. Overall digital photography shows equivalent accuracy to visual estimation and goniometry, but with higher precision than visual estimation.

Smartphone photography utilized to measure wrist range of motion

The purpose was to determine if smartphone photography is a reliable tool in measuring wrist movement. Smartphones were used to take digital photos of both wrists in 32 normal participants (64 wrists) at extremes of wrist motion. The smartphone measurements were compared with clinical goniometry measurements. There was a very high correlation between the clinical goniometry and smartphone measurements, as the concordance coefficients were high for radial deviation, ulnar deviation, wrist extension and wrist flexion. The Pearson coefficients also demonstrated the high precision of the smartphone measurements. The Bland-Altman plots demonstrated 29-31 of 32 smartphone measurements were within the 95% confidence interval of the clinical measurements for all positions of the wrists. There was high reliability between the photography taken by the volunteer and researcher, as well as high inter-observer reliability. Smartphone digital photography is a reliable and accurate tool for measuring wrist range of motion.

LEVEL OF EVIDENCE

II.

Reliability and validity of angle measurements using radiograph and smartphone applications: experimental research on protractor

[Purpose] The present study aimed to demonstrate the following by using measurements for the definite angles provided by the digital protractor: inter-rater reliability and validity in radiograph measurements and smartphone application measurements. [Subjects and Methods] The subject angles were 26 angles between 15° and 180° that were selected randomly using a computer. Three examiners measured the angles using the radiograph and smartphone application. The radiograph was obtained at a position 250 cm from the chest shooting cassette holder. The smartphone photograph was obtained at positions 50, 100, 150, 200, and 250 cm from the holder. [Results] Under all conditions, intra-class correlation coefficients showed 0.999. The correlation coefficient was 0.999 for all conditions. The mean absolute difference to the protractor was ≤0.28° for all conditions. [Conclusion] In comparison with the protractor, radiograph measurements and smartphone application measurements, the results of the present study showed high inter-rater reliability, validity, and small error. The results indicated that radiograph and smartphone application measurements could be used as criteria of validity in angle measurements. It supported the legitimacy of high-quality previous studies that used radiograph measurements as a criterion for validity.

Is digital photography an accurate and precise method for measuring range of motion of the hip and knee?

BACKGROUND

Accurate measurements of knee and hip motion are required for management of musculoskeletal pathology. The purpose of this investigation was to compare three techniques for measuring motion at the hip and knee. The authors hypothesized that digital photography would be equivalent in accuracy and show higher precision compared to the other two techniques.

METHODS

Using infrared motion capture analysis as the reference standard, hip flexion/abduction/internal rotation/external rotation and knee flexion/extension were measured using visual estimation, goniometry, and photography on 10 fresh frozen cadavers. These measurements were performed by three physical therapists and three orthopaedic surgeons. Accuracy was defined by the difference from the reference standard, while precision was defined by the proportion of measurements within either 5° or 10°. Analysis of variance (ANOVA), t-tests, and chi-squared tests were used.

RESULTS

Although two statistically significant differences were found in measurement accuracy between the three techniques, neither of these differences met clinical significance (difference of 1.4° for hip abduction and 1.7° for the knee extension). Precision of measurements was significantly higher for digital photography than: (i) visual estimation for hip abduction and knee extension, and (ii) goniometry for knee extension only.

CONCLUSIONS

There was no clinically significant difference in measurement accuracy between the three techniques for hip and knee motion. Digital photography only showed higher precision for two joint motions (hip abduction and knee extension). Overall digital photography shows equivalent accuracy and near-equivalent precision to visual estimation and goniometry.

Measurement of the knee flexion angle with smartphone applications: Which technology is better?

PURPOSE

The range of motion of the knee is a critical element of clinical assessment. The tested hypothesis was that the measurement of the knee flexion angle measured with two specific smartphone applications using either inclinometer or camera technology was different from the reference measurement with a navigation system designed for total knee arthroplasty (TKA).

METHODS

Ten consecutive patients were selected for navigation-assisted TKA. Five navigated, five inclinometer and five camera measurements of knee flexion angle were obtained for each patient throughout the complete range of motion. The difference, the correlation and the coherence between all measurements and all paired sub-groups were analysed.

RESULTS

There was a strong correlation and a good coherence between the three techniques of measurements, but the knee flexion angle reported by the inclinometer differed substantially from the camera- and navigation-based measurements. The camera-based measurement was clinically identical to the navigated data, with a mean difference of <1° and only 1/50 difference >3°.

CONCLUSION

Camera-based smartphone measurement of the knee range of motion is fit for purpose in a routine clinical setting. The accuracy may be higher than other conventional measurement techniques, allowing a more precise rating of the clinical outcomes after TKA.

LEVEL OF EVIDENCE

II.

The Effect of Patellar Thickness on Intraoperative Knee Flexion and Patellar Tracking in Patients With Arthrofibrosis Undergoing Total Knee Arthroplasty

BACKGROUND

We evaluated the intraoperative effect of patellar thickness on intraoperative passive knee flexion and patellar tracking during total knee arthroplasty (TKA) in patients with preoperative arthrofibrosis and compared them to patients with normal preoperative range of motion (ROM) documented in a prior study.

METHODS

Routine posterior cruciate ligament-retaining TKA was performed in a total of 34 knees, 23 with normal ROM and 11 with arthrofibrosis, defined as ≤100° of passive knee flexion against gravity under anesthesia. Once clinical balance and congruent patellar tracking were established, custom trial patellar components thicker than the standard trial by 2-mm increments (2-8 mm) were sequentially placed and trialed. Passive flexion against gravity was recorded using digital photograph goniometry. Gross mechanics of patellofemoral tracking were visually assessed.

RESULTS

On average, passive knee flexion decreased 2° for every 2-mm increment of patellar thickness (P < .0001), which was similar to patients with normal preoperative ROM. In addition, increased patellar thickness had no gross effect on patellar subluxation and tilt in patients with arthrofibrosis as well as those with normal ROM.

CONCLUSIONS

Patellar thickness had a modest effect on intraoperative passive flexion and no effect on patellar tracking in patients with arthrofibrosis undergoing TKA. There was no marked difference in intraoperative flexion and patellar tracking between patients with arthrofibrosis and patients with normal preoperative ROM.

Comparative analysis of photograph-based clinical goniometry to standard techniques

BACKGROUND

Assessment of joint range of motion (ROM) is an accepted evaluation of disability as well as an indicator of recovery from musculoskeletal injuries. Many goniometric techniques have been described to measure ROM, with variable validity due to inter-rater reliability. In this report, we assessed the validity of photograph-based goniometry in measurement of ROM and its inter-rater reliability and compared it to two other commonly used techniques.

METHODS

We examined three methods for measuring ROM in the upper extremity: manual goniometry (MG), visual estimations (VE), and photograph-based goniometry (PBG). Eight motions of the upper extremity were measured in 69 participants at an academic medical center.

RESULTS

We found visual estimations and photograph-based goniometry to be clinically valid when tested against manual goniometry (r avg. 0.58, range 0.28 to 0.87). Photograph-based measurements afforded a satisfactory degree of inter-rater reliability (ICC avg. 0.77, range 0.28 to 0.96).

CONCLUSIONS

Our study supports photograph-based goniometry as the new standard goniometric technique, as it has been clinically validated, is performed with greater consistency and better inter-rater reliability when compared with manual goniometry. It also allows for better documentation of measurements and potential incorporation into medical records in direct contrast to visual estimation.

Is there a difference in sagittal alignment of Blount's disease between radiographic and clinical evaluation?

BACKGROUND

A procurvatum deformity of the proximal tibia often is seen in patients with Blount's disease. If left untreated, it can lead to progressive angulation in the sagittal plane and altered contact stresses across the knee.

QUESTIONS/PURPOSES

We asked the following questions: (1) Is the mean angle of procurvatum measured from full-length lateral radiographs of the tibia greater than that of procurvatum measured from clinical photographs of the affected lower extremity? (2) Is there a linear relationship between radiographically measured procurvatum and radiographically measured procurvatum?

METHODS

We treated 72 patients surgically for Blount's disease between 1997 and 2012; of those, 29 patients were excluded from this analysis because they did not have adequate photographs or radiographs, leaving 43 patients (60% of the patients treated surgically; 47 limbs total), mean age of 13 years (range, 6-25 years), who underwent surgical realignment for Blount's disease were retrospectively evaluated at a median of 97 months after surgery (range, 24-170 months). Genu procurvatum was measured from full-length lateral radiographs of the tibia and clinical photographs of the affected lower extremity. We then assessed the relationship between radiographically measured procurvatum and clinically measured procurvatum using linear regression analysis.

RESULTS

The mean preoperative radiographically measured procurvatum (12.3°; range -3.1° to 55.2°) was larger than the clinically measured procurvatum (6.0°; range, -1° to 45°; p = 0.024). The mean postoperative radiographically measured procurvatum (4.2°; range -4.8° to 30.3°) was larger than the clinically measured procurvatum (2.1°; range, -2° to 20°; p = 0.041). Preoperatively and postoperatively, radiographically measured procurvatum and clinically measured procurvatum were well correlated (linear regression p < 0.001). After surgical realignment, the mean improvement in radiographically measured procurvatum (8.2°) was larger than that measured for clinically measured procurvatum (3.8°) (p = 0.018).

CONCLUSIONS

In patients with Blount's disease, visual inspection of the extremity can underestimate the procurvatum deformity of the proximal tibia relative to the measurable deformity on radiographs. Furthermore, surgical correction of proximal tibial procurvatum does not lead to clinical hyperextension of the knee.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Development and evaluation of a novel low-cost sensor-based knee flexion angle measurement system

BACKGROUND

Knee injuries form a large part of musculoskeletal trauma in sporting activities and the rehabilitation can require a long period, for both the patients and the specialists, to restore healthy condition. A reliable, portable, and low-cost system that could allow quick, simple, and effective measurement of knee flexion angles would greatly improve the evaluation of the rehabilitation process and the subsequent planning procedure, with meaningful reduction of recovery time and cost.

METHODS

A novel tool for nonstop measurements of knee flexion angles based on the adoption of an elastic sensor embedded in an easy-to-realize wearable kneepad has been proposed. We fully characterized this tool in terms of accuracy, repeatability, and reliability of measure, and validated it against the gold-standard Vicon.

RESULTS

Our tool demonstrated good reproducibility and repeatability among testers (mean range of measures=5.82° ± 1.93°) and high accuracy (root mean square error<1.28°), together with good reliability (intraclass correlation coefficient between 0.80 and 0.91).

CONCLUSIONS

The proposed tool demonstrates good performance, is portable, cheap, easy to use, and allows automatic measurements, so as to be a valuable system for accurate nonstop measurement of knee angles.

CLINICAL RELEVANCE

Our sensor-based measurement system is suitable for the evaluation of the rehabilitation course after knee traumas, because it furnishes a low-cost but accurate monitor of knee flexion movements, during an amount of time as long as desired.

Application of a vibrating device for the prevention of flexion contracture after total knee arthroplasty

Our research team developed a new, heel support-based static and vibrating complementary treatment method for the prevention of flexion contractures often arising after total knee arthroplasty. We examined the efficiency of the method performing a randomized clinical trial with 144 patients undergoing total knee replacement. Seventy-nine patients were treated for 1 week with a generally used continuous passive motion (CPM) device complemented with our new method, which was based on the application of a static and an alternating heel support. The 65 patients in the control group were treated with only a CPM device as in usual clinical practice. The femoro-tibial angle was measured immediately following surgery, and after 1 week of treatment. At the end of the 1 week treatment, the target extension angle (0° ± 5°) was achieved by significantly more patients with the new combined method. This way the elevated heel rest and the vibrating device proved to be a good adjunct treatment along with the CPM used in routine clinical practice in the first place for the prevention of flexion contractures.

Measurement of the knee flexion angle with a Smartphone-application is precise and accurate

We hypothesized that the measurement of the knee flexion angle measured with a specific Smartphone application was different from the reference measurement with a navigation system designed for total knee arthroplasty (TKA). Ten consecutive patients operated on for navigation assisted TKA were selected. Six navigated and 6 Smartphone measurements of knee flexion angle were obtained for each patient. The paired difference between measurements and their correlation were analyzed. The mean paired difference between navigated and Smartphone measurements was -1.1° ± 6.8° (n.s.). There was a significant correlation between both measurements. The coherence between both measurements was good. The intra-observer and inter-observer reproducibility were good. The Smartphone application used may be considered as precise and accurate. The accuracy may be higher than other conventional measurement techniques.

Mid-term Results of Total Knee Arthroplasty Using PFC Sigma RP-F

Purpose

We compared the mid-term results after total knee arthroplasty (TKA) using PFC Sigma RP-F mobile model with PFC Sigma PS fixed model.

Materials and Methods

We analyzed 45 knees that underwent TKA with PFC Sigma RP-Fn (study group) and 45 knees with PFC Sigma PS (control group). The mean follow-up period was 65 months (range, 60-69 months). The evaluation system of the American knee society was used for clinical and radiological assessment. Also, the maximal knee flexion angle was assessed.

Results

The mean maximum flexion angle in the study group (135°) was greater than that in the control group (125°) at the early post-operation & final follow-up period (p=0.033). The range of motion (ROM) in the study group was recovered earlier at the postoperative 6 months, and ROM gain was improved to a greater extent at the final follow-up period (p=0.039). The knee score and function score and radiographic evaluation were no difference between the two groups (p>0.05) at the final follow-up. The two cases of radiolucency in posterior condyle and medial tibial plateau and one case of patellar elongation were seen in the study group.

Conclusions

The PFC Sigma RP-F mobile system appears to facilitate greater maximum flexion angle and ROM gain with two cases of radiolucent line.