Apisan Chinanuvathana

Flexible Adult Acquired Flatfoot Deformity: Comparison Between Weight-Bearing and Non-Weight-Bearing Measurements Using Cone-Beam Computed Tomography

Background: The 3-dimensional nature of adult acquired flatfoot deformity can be challenging to characterize using radiographs. We tested the hypothesis that measurements on weight-bearing (WB) cone-beam computed tomography (CT) images were more useful for demonstrating the severity of the deformity than non-weight-bearing (NWB) measurements. Methods: We prospectively enrolled 12 men and 8 women (mean age, 52 years; range, 20 to 88 years) with flexible adult acquired flatfoot deformity. The subjects underwent cone-beam CT while standing (WB) and seated (NWB), and images were assessed in the sagittal, coronal, and axial planes by 3 independent observers who performed multiple measurements. Intraobserver and interobserver reliabilities were assessed with the Pearson or Spearman correlation and the intraclass correlation coefficient (ICC), respectively. Measurements were compared using paired Student t tests or Wilcoxon rank-sum tests. P < 0.05 was considered significant. Results: We found that overall the measurements had substantial intraobserver and interobserver reliability on both the NWB images (mean ICC, 0.80; range, 0.49 to 0.99) and the WB images (mean ICC, 0.81; range, 0.39 to 0.99). Eighteen of 19 measurements differed between WB and NWB cone-beam CT images, with more pronounced deformities on the WB images. The most reliable measurements, based on intraobserver and interobserver reliabilities and the difference between WB and NWB images, were the medial cuneiform-to-floor distance, which averaged 29 mm (95% confidence interval [CI] = 28 to 31 mm) on the NWB images and 18 mm (95% CI = 17 to 19 mm) on the WB images, and the forefoot arch angle (mean, 13° [95% CI = 12° to 15°] and 3.0° [95% CI = 1.4° to 4.6°], respectively) in the coronal view and the cuboid-to-floor distance (mean, 22 mm [95% CI = 21 to 23 mm] and 17 mm [95% CI = 16 to 18 mm], respectively) and the navicular-to-floor distance (mean, 38 mm [95% CI = 36 to 40 mm] and 23 mm [95% CI = 22 to 25 mm], respectively) in the sagittal view. Conclusions: Measurements analogous to traditional radiographic parameters of adult acquired flatfoot deformity are obtainable using high-resolution cone-beam CT. Compared with NWB images, WB images better demonstrated the severity of osseous derangement in patients with flexible adult acquired flatfoot deformity. Level of Evidence: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Metal Artifact Reduction MRI for Total Ankle Replacement Sagittal Balance Evaluation

BACKGROUND Restoration of anatomical relationship between talus and tibia is crucial for longevity of total ankle replacement (TAR). Weight-bearing (WB) radiographs are the standard for evaluating the sagittal balance alignment, but are prone to rotational misalignment and altered measurements. Metal artifact reduction sequence (MARS) MRI allows visualization of periprosthetic landmarks and alignment of the image plane to the true sagittal axis of the implant. The purpose of this study was to compare TAR sagittal balance measurements on MARS MRI and WB radiographs. METHODS Twenty-three subjects with TAR [10 men/13 women, age 60 (41-73) years; 13 (3-24) months post-op] underwent MARS MRI and standard lateral WB radiographs. Standardized MARS MR images were aligned to the sagittal talar component axis. Three observers performed sagittal balance alignment measurements twice in an independent, random and blinded fashion. Lateral Talar Station (LTS), tibial axis-to-talus (T-T) ratio and normalized tibial axis-to-lateral-process (T-L) distance were measured. Concordance correlation coefficients (CCC) and intraclass correlation coefficients (ICC) were used for statistical analysis. In addition, mixed effects linear models were employed to assess overall concordance of the two image types. RESULTS The intraobserver agreement was excellent for radiographic (CCC=0.96) and MRI (CCC=0.90-0.97) measurements. Interobserver agreements were good-to-excellent with overall slightly higher agreements for MRI (ICC=0.78-0.94) than radiography (ICC=0.78-0.90) measurements. The T-T ratios of radiographs and MRI showed a high degree of concordance, whereas LTS was significantly lower on MRI when compared with radiographs, and T-L distance showed notable disagreement between the two imaging types. CONCLUSION Sagittal balance measurements performed on standardized weight-bearing radiographs and standardized MARS MRI demonstrate substantial correlation and similarity. Given its high intra and interobserver agreement, MARS MRI may be helpful for the evaluation of TAR sagittal balance. LEVEL OF EVIDENCE Level II - Prospective Comparative Study.

Outcomes of flexor digitorum longus (FDL) tendon transfer in the treatment of Achilles tendon disorders

BACKGROUND In patients with chronic Achilles tendon disorders, Achilles tendon debridement can be supplemented with a tendon transfer, with the flexor hallucis longus tendon (FHL) transfer representing the most common used technique. Our study describes clinical and functional results of patients treated with flexor digitorum longus (FDL) tendon transfer in the treatment of patients with chronic Achilles tendon disorders. METHODS Retrospective study of prospectively collected data of thirteen patients (15 feet) that underwent FDL tendon transfer as part of the treatment of chronic Achilles tendon disorders. Preoperative and postoperative assessment included visual analogue score (VAS) for pain, SF-36 survey and lower extremity functional scale (LEFS). The average follow-up was 26.4 (range, 14-56) months. Patients were also assessed for ability to perform single leg heel rise test, muscle power for plantar flexion of the lesser toes, surgical scar condition and associated complications. RESULTS At final follow-up, we found significant postoperative improvement in VAS score (6.6 ± 2.99 vs 1.06 ± 1.43; p < .0001), SF-36 physical component summary (PCS) (28.20 ± 10.71 vs 45.04 ± 11.19; p < .0001) and LEFS (36.13 ± 20.49 vs 58.73 ± 18.19; p < .0001). Twelve patients (92%) could perform a single leg heel rise test in the operated extremity, although there was significant difference when comparing operated and uninvolved sides (4.86 ± 3.36 cm vs 7.18 ± 3.40 cm; p = .0002). One patient reported weakness for plantar flexion of the lesser toes, without balance or gait disturbances. Two patients (2 feet, 13.3%) had superficial infections and one patient (one foot, 6.6%) needed operative debridement for a deep infection. CONCLUSIONS FDL tendon transfer represent an operative alternative in the treatment of chronic Achilles tendon disorders. Our study showed good clinical outcomes with low complications and donor site morbidity. LEVEL OF EVIDENCE Observational study, case series - level IV.

Outcomes of Flexor Digitorum Longus (FDL) Tendon Transfer for the Treatment of Chronic Achilles Tendinopathy

Category: Hindfoot, Sports Introduction/Purpose: Flexor hallucis longus (FHL) tendon transfer is a common surgical technique used for augmentation during the surgical treatment of chronic Achilles tendinopathy and reconstruction. Flexor digitorum longus (FDL) tendon transfer represents a viable surgical alternative for patients with failed FHL transfers or athletes where compromise of the hallux push off strength could negatively impact their level of activity. There is no reported clinical outcome data about this technique in the current literature. Our study describes the clinical and functional results after FDL tendon transfer for the treatment of patients with chronic Achilles tendinopathy. Methods: We retrospectively assessed prospectively collected data on patients that underwent FDL tendon transfer in the treatment of chronic Achilles tendinopathy (March 2012 - March 2015). Charts were reviewed for clinical data, associated treatments and complications. Preoperative assessment included the Visual Analogue Score (VAS), SF-36 health status survey and the lower extremity functional scale (LEFS). At final follow up we evaluated pain level, range of motion of the ankle and the toes, ability to perform single leg raise and toe walking, calf atrophy and complications. Postoperative outcomes were assessed by Visual Analogue Score (VAS), SF-36 health survey, Lower Extremity Functional Scale (LEFS), Foot Function Index (FFI), VISA-A score and the Foot and Ankle Ability Measure (FAAM). Fifteen patients (seventeen feet), 6 males and 9 females, mean age of 53.6 years (27- 76 years) and an average body mass index of 31.4 kg/m2 (20.5 to 45.4 kg/m2) were included in the study. Results: Mean follow-up was 27.5 months (15-49). Four patients (6 feet) had prior surgeries, including two patients with failed FHL transfer. We found significant clinical improvement when comparing pre-operative and postoperative VAS scores (6.0±3.3 versus 1±1.36; p<0.001), SF-36 physical component summary (28.2±10.7 versus 45.0±11.1; p<0.002) and LEFS (36.4±22 versus 57.9±20.5; p<0.011). At final follow up, 6/7 patients (86%) returned to prior levels of recreational sport activities. No differences were found on single leg raise test when compared to uninvolved side. One patient reported weakness for plantar flexion of the toes, without gait complaints. Mean VISA-A was 52.6 points (15-85), Foot Function Index (FFI) 21.2% (0-65%) and FAAM 86.2% (55.3-100%) for the FAAM. Three patients had superficial infection and two patients had deep infection, requiring surgical debridement. Conclusion: FDL tendon transfer represents a safe surgical alternative as a method of augmentation during the treatment of chronic Achilles tendinopathy. Our study showed comparable clinical and functional outcomes to FHL tendon transfer and minimal complications or donor site morbidity.

Hindfoot Alignment of Adult Acquired Flatfoot Deformity: A Comparison of Clinical Assessment and Weightbearing ConeBeam CT Examinations

Category: Hindfoot Introduction/Purpose: Assessment of hindfoot alignment in adult acquired flatfoot deformity (AAFD) can be challenging. Clinical judgment and radiograph studies while important may not represent the accurate valgus alignment of the affected patients. Weightbearing (WB) ConeBeam CT (CBCT) is an emerging imaging modality that may potentially better demonstrate the three-dimensional (3D) deformity, facilitating visualization of important soft-tissue and bony landmarks and helping in surgical planning. Based on the relative position of bone and soft-tissue axes, different measurements of hindfoot alignment can be obtained with CT images. Therefore, we compared clinical assessment of hindfoot valgus alignment in AAFD patients with different possible measurements performed on WB CBCT images. Methods: In this prospective, IRB-approved study, 20 patients (20 feet, 15 right and 5 left) with clinical diagnosis of flexible AAFD were included. There were 12 males and 8 females, with a mean age of 52.2 years (range, 20 – 88 years of age), and average BMI of 30.35 kg/m2 (range, 19.00 – 46.09 kg/m2). Patients underwent clinical assessment of hindfoot alignment as well as WB CBCT. Two independent and blinded foot and ankle board-certified surgeons performed different hindfoot alignment measurements on the WB CBCT images that included: 3D “clinical” alignment; Achilles tendon axis/calcaneal tuberosity angle; angles formed between the tibial axis and the calcaneal tuberosity, calcaneal axis and line connecting midpoint of subtalar joint and most inferior part of calcaneal tuberosity. Positive values were considered valgus alignment. Mean differences between the measurements modalities were compared by paired T-test. Intra- and Inter-observer reliability for the WB CBCT measurements were calculated using Pearson correlation. Results: The mean clinical hindfoot valgus measured was 15.15o (SD 7.7o). It was found to be significantly different from the mean values of all WB CBCT angles modalities: 3D “clinical” alignment (10.42o, p < 0.015); Achilles tendon/calcaneal tuberosity angle (2.96o, p < 0.0001); tibial axis/calcaneal tuberosity angle (5.42o, p < 0.0001); tibial axis/subtalar joint angle (7.52o, p < 0.0001) and tibial axis/calcaneal axis angle (20.39o, p < 0.017). We found an excellent intra-observer agreement for all WB CBCT 3D measurements (range, 0.8863 – 0.9713, p < 0.0001). There was also good to excellent inter-observer reliability, with the exception of the 3D “clinical” alignment (r=0.450, p < 0.04), that showed moderate correlation. Conclusion: The use of 3D WB CBCT imaging can help characterize the valgus hindfoot alignment in patients with adult acquired flatfoot deformity. We found the different CBCT measurements modalities to be reliable and repeatable, and to significantly differ from the clinical evaluation of hindfoot valgus alignment.

Comparison between Weight Bearing Radiographs and Weight Bearing ConeBeam CT Examinations in the Assessment of Adult Acquired Flatfoot Deformity

Category: Hindfoot Introduction/Purpose: Adult acquired flatfoot deformity (AAFD) represents a biomechanical derangement involving the three- dimensional (3D) midfoot and hindfoot osseous complex, and can be challenging to optimally characterize using conventional two- dimensional (2D) plain radiographs. Weightbearing (WB) ConeBeam CT (CBCT) can better demonstrate the deformity of the 3D structures during WB. Therefore, we compared validated AAFD measurements between WB conventional radiographs and WB CBCT images. Methods: In this prospective, IRB approved and HIPAA compliant study, 20 patients (20 feet, 15 right and 5 left) with clinical diagnosis of flexible AAFD were included, 12 males and 8 females, with a mean age of 52.2 years (range, 20 to 88 years of age), and average BMI of 30.35 kg/m2 (range, 19.00 to 46.09 kg/m2). Involved feet underwent standing (WB) anteroposterior (AP) and lateral radiographs, and were also scanned by WB CBCTs. Both imaging modalities were assessed with traditional AAFD measurements obtained at sagittal (lateral view on radiograph) and axial (anteroposterior view on radiograph) planes using predefined anatomical landmarks, by two independent and blinded foot and ankle fellowship-trained observers. Intra- and Inter- observer reliabilities for both imaging modalities were calculated using Pearson correlation. WB radiograph and WB CBCT measurements were compared by T-Test of the means. P- values < 0.05 were considered significant. Results: There was good to excellent intra and inter-observer agreements for most of the measurements on both radiographs and WB CBCT images, with slightly better results favoring WBCT measurements. When comparing WB radiographs and WB CBCT images, we found significant differences in the mean values for some of the measurements, including: talus-first metatarsal angle in the sagittal plane (11.34° x 21.73°, p<0.0001), navicular-medial cuneiform angle (13.19° x 7.63°, p<0.0004), medial cuneiform to floor distance (6.70 mm x 5.50 mm, p<0.0003) and navicular to floor distance (31.34 mm x 23.22 mm, p<0.0001). No significant differences were found when measuring: talus-first metatarsal angle in the axial plane, talar uncoverage angle, cuboid to floor distance and calcaneal inclination angle. Conclusion: Traditional adult acquired flatfoot deformity radiographic measurements are obtainable using high resolution 3D WB CBCT imaging. Measurements performed on WB CBCT have similar intra-observer and overall higher inter-observer reliability when compared to WB radiographs. The statistically significant differences found in some of the measurements, when comparing both imaging techniques, might be related to a better characterization of the three-dimensional deformity on WB CBCT images.

Metal Artifact Reduction MRI for Sagittal Balance Evaluation of Total Ankle Arthroplasty

Category: Ankle Arthritis Introduction/Purpose: Surgical restoration of the anatomical relationship between talus and tibia is considered crucial for longevity of total ankle arthroplasty (TAA). Weight-bearing (WB) radiographs are the current standard for evaluating the sagittal balance alignment, which are, however, prone to rotational misalignment and potentially altered measurements. Metal artifact reduction sequence (MARS) MRI is a cross-sectional technique that minimizes implant-induced artifacts and affords the visualization of bone-implant interfaces and periprosthetic bone without distortions. Although not weight-bearing, MARS MRI offers the ability to align the image plane to the true sagittal axis of the talar implant and anatomically correct measurements. Therefore, the purpose of this study was to compare sagittal balance alignment measurements on MARS MR images and standard WB radiographs in patients with TAA. Methods: In this IRB-approved, prospective study, 23 subjects [10 men/13 women, age 60(41-73) years; 13(3-24) months post- op] underwent MARS MRI and standard lateral WB radiographs. Standardized MARS MR images were obtained in alignment to the sagittal talar component axis and use of a boot-shaped MRI coil. Maximum-intensity-projection MR images that resemble lateral radiographs were created to bring anatomic landmarks, such as lateral talar process, talonavicular joint line, talar implant, tibial shaft, and posterior talus into one single image. Three board-certified foot ankle surgeons performed sagittal balance alignment measurements twice in an independent, random and blinded fashion. The second set of measurements was obtained 1 months after the first assessment. In accordance with published measurements, lateral talar station (LTS), tibial axis-to-talus (T-T) ratio, and normalized tibial axis-to-lateral-process (T-L) distance were measured. Pearson correlation coefficient (r), Concordance-Correlation-Coefficient (CCC) and Intraclass-Correlation-Coefficient (ICC) were used for statistical analysis. Bonferroni-corrected p-values ≤ 0.01 were considered significant. Results: The intra-observer agreement was excellent for radiographic (CCC = 0.93 - 0.97) and MRI (CCC = 0.90 - 0.97) measurements. Inter-observer agreements were good-to-excellent with overall higher agreements for MRI (ICC = 0.76 - 0.93) than for radiography (ICC = 0.58 - 0.95) measurements. There was statistically significant inter-method correlation between radiographic and MRI measurements including LTS (r=0.83, p < 0.001), T-T ratio (r=0.86, p < 0.001) and normalized T-L distance (r=0.72, p < 0.001). The T-T ratios of radiographs and MRI were statistically not different (p=0.36), whereas LTS and normalized T-L distance were significantly lower on MR images when compared with radiographs (p < 0.001). Conclusion: Sagittal balance measurements performed on standardized weight-bearing radiographs and standardized MARS MR images demonstrate substantial correlation and similarity. Given its high inter- and intra-observer agreement, MARS MRI may be helpful for the evaluation of sagittal balance following TAA.