Anatomical study of the medial calcaneal nerve using high-resolution ultrasound.

OBJECTIVES: To determine whether high-resolution ultrasound (US) can identify the course and relations of the medial calcaneal nerve (MCN). METHODS: This investigation was initially undertaken in eight cadaveric specimens and followed by a high-resolution US study in 20 healthy adult volunteers (40 nerves) by two musculoskeletal radiologists in consensus. The location and course of the MCN as well as its relationship to adjacent anatomical structures were evaluated. RESULTS: The MCN was consistently identified by US along its entire course. The mean cross-sectional area of the nerve was 1 mm2 (range 0.5-2). The level at which the MCN branched from the tibial nerve was variable, located a mean of 7 mm (range - 7-60) proximal to the tip of the medial malleolus. At the level of the medial retromalleolar fossa, the MCN was located inside the proximal tarsal tunnel a mean of 8 mm (range 0-16) posterior to the medial malleolus. More distally, the nerve was depicted in the subcutaneous tissue at the surface of the abductor hallucis fascia with a mean direct distance to the fascia of 1.5 mm (range 0.4-2.8). CONCLUSIONS: High-resolution US can identify the MCN at the level of the medial retromalleolar fossa, as well as more distally in the subcutaneous tissue at the surface of the abductor hallucis fascia. In the setting of heel pain, precise sonographic mapping of the MCN course may enable the radiologist to make diagnosis of nerve compression or neuroma, and perform selective US-guided treatments. CLINICAL RELEVANCE STATEMENT: In the setting of heel pain, sonography is an attractive tool for diagnosing compression neuropathy or neuroma of the medial calcaneal nerve, and enables the radiologist to perform selective image-guided treatments such as diagnostic blocks and injections. KEY POINTS: • The MCN is a small cutaneous nerve which rises from the tibial nerve in the medial retromalleolar fossa to the medial side of the heel. • The MCN can be depicted by high-resolution ultrasound along its entire course. • In the setting of heel pain, precise sonographic mapping of the MCN course may enable the radiologist to make diagnosis of neuroma or nerve entrapment, and perform selective ultrasound-guided treatments such as steroid injection or tarsal tunnel release.

Ultrasound and MR imaging of peripheral nerve tumors: the state of the art.

Peripheral nerve sheath tumors are a heterogeneous subgroup of soft tissue tumors that either arise from a peripheral nerve or show nerve sheath differentiation. On imaging, direct continuity with a neural structure or location along a typical nerve distribution represents the most important signs to suggest the diagnosis. Ultrasound and magnetic resonance imaging are the best modalities to evaluate these lesions. First, it is necessary to differentiate between a true tumor and a non-neoplastic nerve condition such as a neuroma, peripheral nerve ganglion, intraneural venous malformation, lipomatosis of nerve, or nerve focal hypertrophy. Then, with a combination of clinical features, conventional and advanced imaging appearances, it is usually possible to characterize neurogenic tumors confidently. This article reviews the features of benign and malignant peripheral nerve sheath tumors, including the rare and recently described tumor types. Furthermore, other malignant neoplasms of peripheral nerves as well as non-neoplastic conditions than can mimick neurogenic tumor are herein discussed.

Vertebral trabecular bone texture analysis in opportunistic MRI and CT scan can distinguish patients with and without osteoporotic vertebral fracture: A preliminary study.

PURPOSE: To investigate the potential of texture parameters from opportunistic MRI and CT for the detection of patients with vertebral fragility fracture, to design a decision tree and to compute a Random Forest analysis for the prediction of fracture risk. METHODS: One hundred and eighty vertebrae of sixty patients with at least one (30) or without (30) a fragility fracture were retrospectively assessed. Patients had a DXA, an MRI and a CT scan from the three first lumbar vertebrae. Vertebrae texture analysis was performed in routine abdominal or lumbar CT and lumbar MRI using 1st and 2nd order texture parameters. Hounsfield Unit Bone density (HU BD) was also measured on CT-scan images. RESULTS: Twelve texture parameters, Z-score and HU BD were significantly different between the two groups whereas T score and BMD were not. The inter observer reproducibility was good to excellent. Decision tree showed that age and HU BD were the most relevant factors to predict the fracture risk with a 93 % sensitivity and 56 % specificity. AUC was 0.91 in MRI and 0.92 in CT-scan using the Random Forest analysis. The corresponding sensitivity and specificity were 72 % and 93 % in MRI and 83 and 89 % in CT. CONCLUSIONS: This study is the first to compare texture indices computed from opportunistic CT and MR images. Age and HU-BD together with selected texture parameters could be used to assess risk fracture. Machine learning algorithm can detect fracture risk in opportunistic CT and MR imaging and might be of high interest for the diagnosis of osteoporosis.

Osteoid Osteoma: Percutaneous CT-guided Cryoablation Is a Safe, Effective, and Durable Treatment Option in Adults.

Background Cryoablation is playing an increasing role in the percutaneous treatment of bone tumors. However, despite its potential advantages over heat-based ablation techniques, the clinical safety and efficacy of cryoablation have not been established for osteoid osteoma treatment. Purpose To evaluate percutaneous CT-guided cryoablation for the treatment of osteoid osteoma in young patients and adults. Materials and Methods This retrospective study reviewed data from 50 consecutive patients who underwent percutaneous CT-guided cryoablation for the treatment of osteoid osteoma between January 2013 and June 2019 in a single institution. In 30 of 50 patients (60%), the procedure was carried out with the patient under local anesthesia and conscious sedation, with the cryoprobe covering the lesion from an extraosseous position, avoiding direct penetration of the nidus. Clinical and radiologic features, procedure-related data, visual analog scale (VAS) pain scores, complications, and overall success rate were evaluated. Statistical analyses were performed by using the nonparametric Friedman test and Wilcoxon signed rank test for repeated measures. Results Fifty patients (median age, 24 years; interquartile range [IQR], 19-38 years; 31 men) underwent CT-guided cryoablation for the treatment of osteoid osteoma, with a 96% (48 of 50 patients) overall clinical success rate. Of the two patients without clinical success, one patient had incomplete pain relief and the other experienced a recurrence of osteoid osteoma at 11 months, which was successfully treated with a second cryoablation procedure. The median VAS pain score was 8 (IQR, 7-8) before the procedure and 0 (IQR, 0-1; P < .001) after the procedure at both primary (6 weeks) and secondary (18-90 months) follow-up. Three of the 50 patients had minor complications (6%); no major complications were reported. Conclusion Osteoid osteoma was safely, effectively, and durably treated with CT-guided percutaneous cryoablation. In the majority of patients, treatment could be performed without general anesthesia, with the cryosphere covering the nidus from an extraosseous position. © RSNA, 2021.

Stenosing tenosynovitis of the extensor digitorum tendons of the hand: clinical and sonographic features.

OBJECTIVE: To describe the ultrasound (US) features of 18 patients with extensor digitorum communis stenosing tenosynovitis (EDCST). MATERIALS AND METHODS: A retrospective search in the radiologic information systems of two separate Institutions was performed to identify all patients presenting EDCST between January 2010 and September 2019. A total of 18 patients (ten males and eight females; mean age, 57.4 years) were identified and included. Sonographic examinations were retrospectively reviewed by two senior radiologists to assess morphologic changes and power Doppler activity of the extensor retinaculum (ER) and of the extensor digitorum communis (EDC) tendons and sheath. The presence of dynamic impingement between the EDC and the ER was evaluated using video clip records. RESULTS: At the ultrasound, all patients (18/18; 100%) presented thickening of both the ER and EDC tendons associated with EDC tendon sheath effusion. Power Doppler hyperemia of the ER was inconstant and observed in 11 cases (11/18; 61.1%) as tendon sheath effusion observed in 16 cases (16/18; 88.9%). A cyst located inside the EDC of the index finger was observed in three of these patients (3/18; 17%). Dynamic examination showed impingement of the EDC against the ER during active tendon extension in all patients (18/18; 100%). Four of these patients (4/18; 22%) underwent surgery allowing diagnosis confirmation and release of EDCST, while the remaining fourteen patients (14/18; 78%) were either treated conservatively or using US-guided steroid injection. CONCLUSION: US findings of EDCST include thickening of the ER and EDC tendons, EDC tendon sheath effusion, and in some cases presence of an EDC intratendinous cyst. Impingement of the EDC tendons against the ER is well demonstrated using dynamic US.

Acral FibroChondroMyxoid tumor: imaging features of a new entity.

"Acral FibroChondroMyxoid tumor" (AFCMT) is a recently described distinctive subtype of acral soft tissue tumor that typically arises on the fingers and toes. We herein present the unreported imaging features of AFCMT in a 44-year-old woman. This otherwise healthy patient was referred for a painful, slow-growing, soft tissue mass in the middle finger of her right hand. Initial radiographs and computed tomography showed a small lesion centered in the soft tissue of the ulnar aspect of the proximal phalanx, associated with scalloping of the underlying bone. Magnetic resonance imaging confirmed the presence of a well-circumscribed soft tissue tumor that exhibited relatively high T2-weighted signal intensity and marked enhancement after contrast administration. Subsequent excisional biopsy was performed. Histologically, the tumor was characterized by an abundant stroma displaying fibrous, chondroid, and myxoid areas. By immunohistochemistry, tumor cells stained for CD34, ERG, and focally S100 protein. RNA-sequencing allowed detection of THBS1-ADGFR5 gene fusion which confirmed the diagnosis of AFCMT. At 2-year follow-up, the patient remains free of recurrence. AFCMT is a previously unrecognized entity that may mimic chondroma and should be considered in the differential diagnosis of soft tissue tumors with cartilaginous or myxoid stroma in the extremities.

Flat-panel CT arthrography for cartilage defect detection in the ankle joint: first results in vivo.

OBJECTIVES: The purpose of this study was to compare the diagnostic performance of flat-panel computed tomography (FPCT) arthrography for cartilage defect detection in the ankle joint to direct magnetic resonance (MR) arthrography using multidetector computed tomography (MDCT) arthrography as the reference standard. METHODS: Twenty-seven patients with specific suspicion of articular cartilage lesion underwent ankle arthrography with injection of a mixture of diluted gadolinium and iobitridol and were examined consecutively with the use of FPCT, MDCT, and 1.5 T MR imaging. FPCT, MDCT, and MR arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle, eight articular cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial plafond, lateral tibial plafond, and fibular malleolus. Findings at FPCT and MR were compared with MDCT assessments in 216 cartilage areas. RESULTS: For the detection of cartilage defects, FPCT demonstrated a sensitivity of 97%, specificity of 95%, and accuracy of 96%; and MR arthrography showed a sensitivity of 69%, specificity of 94%, and accuracy of 87%. FPCT and MR arthrography presented almost perfect agreement (κ = 0.87) and moderate agreement (κ = 0.60), respectively, with MDCT arthrography. Mean diagnostic confidence was higher for FPCT (2.9/3) than for MR (2.3/3) and MDCT (2.7/3) arthrography. CONCLUSIONS: FPCT demonstrated better accuracy than did 1.5 T MR arthrography for cartilage defect detection in the ankle joint. Therefore, FPCT should be considered in patients scheduled for dedicated imaging of ankle articular cartilage.

Anatomical study of the medial plantar proper digital nerve using ultrasound.

PURPOSE: To determine whether ultrasound allows precise assessment of the course and relations of the medial plantar proper digital nerve (MPPDN). MATERIALS AND METHODS: This work was initially undertaken in six cadaveric specimens and followed by a high-resolution ultrasound study in 17 healthy adult volunteers (34 nerves) by two musculoskeletal radiologists in consensus. Location and course of the MPPDN and its relationship to adjacent anatomical structures were analysed. RESULTS: The MPPDN was consistently identified by ultrasound along its entire course. Mean cross-sectional area of the nerve was 0.8 mm2 (range 0.4-1.4). The MPPDN after it branches from the medial plantar nerve was located a mean of 22 mm (range 19-27) lateral to the medial border of the medial cuneiform. More distally, at the level of the first metatarsophalangeal joint, mean direct distances between the nerve and the first metatarsal head and the medial hallux sesamoid were respectively 3 mm (range 1-8) and 4 mm (range 2-9). CONCLUSION: The MPPDN can be depicted by ultrasonography. Useful bony landmarks for its detection could be defined. Precise mapping of its anatomical course may have important clinical applications. KEY POINTS: • The medial plantar proper digital nerve (MPPDN) rises from the medial plantar nerve to the medial side of the hallux. • Because of its particularly long course and superficial position, the MPPDN may be subject to trauma, resulting in a condition known as Joplin's neuroma. • The MPPDN can be clearly depicted by ultrasound along its entire course. Precise mapping of its anatomical course may have important clinical applications.

Partial anterior tunnel syndrome: a retrospective analysis of ultrasound findings in four surgically proven cases.

We present the cases of four patients (two men and two women, mean age of 48.5 years) with surgically confirmed partial anterior tarsal syndrome, diagnosed by ultrasound. All patients reported pain in the dorsal aspect of the forefoot radiating to the first intermetatarsal space. Ultrasound showed compression of the medial branch of the deep fibular nerve by the extensor hallucis brevis tendon at the level of the Lisfranc joint, associated with a hypoechoic neuroma. The ultrasound allowed a correct diagnosis to be obtained, which was not evident from clinical examination or by standard radiographs (four patients) or MRI (three patients). Surgery confirmed the sonographic findings, and all patients showed complete recovery.

Percutaneous cryoablation for the treatment of osteoid osteoma in the adult population.

PURPOSE: To evaluate the technical feasibility and efficacy of percutaneous cryoablation for the treatment of osteoid osteoma (OO) in adults. METHODS AND MATERIALS: 21 patients (12 male and nine female; mean age, 29.9 years) who underwent CT-guided percutaneous cryoablation for the treatment of OO were retrospectively evaluated. Procedures were carried out under local anaesthesia and conscious sedation in 13 patients, and under general anaesthesia in eight patients. Then, the ablation zone was evaluated with post-procedure magnetic resonance imaging at 6 weeks. Clinical outcome was assessed using a visual analogue scale (VAS) to evaluate severity of pain before procedure, as well as at primary (6 weeks) and secondary follow-up (6-40 months). RESULTS: All procedures were technically successful. Median VAS scores were: 8 (range, 5-10) before procedure and after procedure, respectively, 0 (range, 0-2; p < .0001) and 0 (range, 0-7; p < .0001) at primary and secondary follow-up. There were three minor complications (14.3%) and no major complication. A single patient reported symptom recurrence (4.8%) at secondary follow-up and successfully underwent a second cryoablation procedure. CONCLUSION: CT-guided percutaneous cryoablation is safe and effective in the treatment of OO in adults, and can be accomplished without general anaesthesia in selected cases. KEY POINTS: • CT-guided percutaneous cryoablation of osteoid osteoma is safe and effective • Cryoablation allows precise visual control of the aggregated iceball during procedure • Percutaneous cryoablation can be accomplished without general anaesthesia in selected cases • Another advantage of cryoablation is reduction of immediate postprocedural pain • Post-procedure MRI is helpful in the evaluation of technical success.

Soft Tissue Masses of the Knee Related to a Focal Defect of the Lateral Patellar Retinaculum.

We report on the imaging features of 6 soft tissue masses in the anterolateral aspect of the knee related to a focal defect of the lateral patellar retinaculum. In 4 patients (3 female and 1 male; 6-65 years) presenting with nontender palpable soft tissue masses in the anterolateral aspect of their knees, ultrasonography showed a focal defect of the lateral patellar retinaculum with herniation of the Hoffa fat pad, which was only visible in flexion. A magnetic resonance imaging examination performed in 1 case confirmed the defect in the lateral patellar retinaculum but did not show a mass, as the knee was examined only at 10° of flexion. The 2 remaining patients (one male and 1 female; 62 and 55 years) presented with soft tissue masses in their anterolateral knees in both flexion and extension. These masses were related respectively to a lipoma of the Hoffa fat pad and to a ganglion cyst, both herniated through a defect of the lateral patellar retinaculum. Our cases suggest that a focal defect of the lateral patellar retinaculum may be a route for Hoffa fat pad herniation as well as a route for superficial extension of infrapatellar fat lesions such as lipomas and ganglion cysts.

Mechanical strains passing through the acetabular labrum modify its shape during hip motion: an anatomical study.

PURPOSE: The function of the hip labrum during hip motion remains poorly known. Our hypothesis was that acetabular labrum will deform and change its shape during adduction to abduction movement consecutively to variation of strains passing from the acetabulum to the femoral head. An ex vivo anatomical study was conducted to analyse the morphological parameters variation of the mid-portion of the labrum (length, thickness, shape, deformation) as well as femoro-labral strains during hip adduction to abduction movement. METHODS: Ten fresh-frozen, unpaired human cadaver hemi-pelvises were obtained. To best approximate the clinical reality, fresh-frozen cadaver tissues were utilized. The hemi-pelvises were split sagittally in two equal parts through a plane crossing the femoral neck and femoral head centres. The hemi-pelvises were rigidly mounted on a test platform using a custom-made fixture, and a seven hundred Newton load was applied through the iliac wing, with a unidirectional movement (adduction/abduction) of the acetabulum above the fixed femur. Variations of strain passing from the labrum to the femoral head or neck were analysed using captors fixed on the acetabular edge. RESULTS: From 20° to 40° of abduction labral length decreased from a median of 5.8 (5.5-6.4 mm) to 4.6 (4-5.4 mm), labral edge angle increased from a median of 33.1 (31.1°-40°) to 52.3 (41.4°-58.8°), labral sectional area decreased from a median of 22.1 (17-27.1 mm2) to 14.2 (12-16.8 mm2) all p = 0.001. Femoro-labral strains were maximal at 40° of abduction [median 0.1 N mm-2 (0.1-3.1 N mm-2)] and minimal at 30° adduction (median 0 N mm-2 (0-0.1 N mm-2) and p = 0.001). CONCLUSION: The morphological variations of the mid-portion of the labrum during hip motion reflect strains passing from the labrum to the femoral head. Those elements may provide clues to understand the mechanical role of the labrum during abduction. The acetabular labrum bears a direct mechanical role during hip motion, thus resecting the hip's labrum during surgery might be detrimental for hip joint's biomechanics as it might modify strains distribution between the acetabulum and femur.

C-arm flat-panel CT arthrography of the shoulder: Radiation dose considerations and preliminary data on diagnostic performance.

OBJECTIVES: To investigate radiation dose and diagnostic performance of C-arm flat-panel CT (FPCT) versus standard multi-detector CT (MDCT) shoulder arthrography using MRI-arthrography as reference standard. METHODS: Radiation dose of two different FPCT acquisitions (5 and 20 s) and standard MDCT of the shoulder were assessed using phantoms and thermoluminescence dosimetry. FPCT arthrographies were performed in 34 patients (mean age 44 ± 15 years). Different joint structures were quantitatively and qualitatively assessed by two independent radiologists. Inter-reader agreement and diagnostic performance were calculated. RESULTS: Effective radiation dose was markedly lower in FPCT 5 s (0.6 mSv) compared to MDCT (1.7 mSv) and FPCT 20 s (3.4 mSv). Contrast-to-noise ratios (CNRs) were significantly (p < 0.05) higher in FPCT 20-s versus 5-s protocols. Inter-reader agreements of qualitative ratings ranged between к = 0.47-1.0. Sensitivities for cartilage and rotator cuff pathologies were low for FPCT 5-s (40 % and 20 %) and moderate for FPCT 20-s protocols (75 % and 73 %). FPCT showed high sensitivity (81-86 % and 89-99 %) for bone and acromioclavicular-joint pathologies. CONCLUSION: Using a 5-s protocol FPCT shoulder arthrography provides lower radiation dose compared to MDCT but poor sensitivity for cartilage and rotator cuff pathologies. FPCT 20-s protocol is moderately sensitive for cartilage and rotator cuff tendon pathology with markedly higher radiation dose compared to MDCT. KEY POINTS: • FPCT shoulder arthrography is feasible with fluoroscopy and CT in one workflow. • A 5-s FPCT protocol applies a lower radiation dose than MDCT. • A 20-s FPCT protocol is moderately sensitive for cartilage and tendon pathology.

Correlation between the retroversion of the humeral head and the orientation of the intertubercular sulcus: a CT scan anatomical study.

PURPOSE: The purpose was to study the anatomy of the humeral head, more specifically the retroversion of the humeral head and the orientation of the intertubercular sulcus, using CT scan, and to make correlations between those two entities of the proximal humerus. METHODS: Sixty dry adult humeri from an osteological collection underwent CT scan from the proximal to the distal extremity. The measurements obtained by CT-reformation were recorded by two independent radiologists. We determined the humeral head axis, the transepicondylar axis, the retroversion of the humeral head, and the orientation of the intertubercular sulcus (ITS). Statistical analysis using SPSS determined the Pearson correlation coefficient. RESULTS: The CT scan measurements were similar to those in the literature, and thus allowed us to validate CT scan assessment. Statistical analysis showed a significant reverse correlation [the coefficient of correlation was -0.37 (p = 0.004)] between the retroversion of the humeral head and the orientation of the intertubercular sulcus: the more the retroversion of the humeral head increases, the more the angle of the orientation of the ITS decreases. CONCLUSIONS: To the best of our knowledge, this reverse correlation between the retroversion of the humeral head and the orientation of the intertubercular sulcus has never been described. This new anatomical data might be helpful for orthopedic surgery.

Diagnostic performance of flat-panel CT arthrography for cartilage defect detection in the ankle joint: comparison with MDCT arthrography with gross anatomy as the reference standard.

OBJECTIVE: The purpose of this study is to compare the diagnostic performance and radiation exposure of flat-panel CT arthrography for cartilage defect detection in the ankle joint to standard MDCT arthrography, using gross anatomy and thermoluminescent dosimetry as reference standards. MATERIALS AND METHODS: Ten cadaveric ankle specimens were obtained from individuals who had willed their bodies to science. Five milliliters of a mixture of diluted ioxaglate and saline were injected. Specimens were examined consecutively with the use of flat-panel CT and MDCT. Radiation doses of flat-panel CT and MDCT were recorded using thermoluminescent dosimeters. Flat-panel CT and MDCT arthrography examinations were blinded and randomly evaluated by two musculoskeletal radiologists in consensus. In each ankle specimen, eight cartilage areas were assessed separately: medial talar surface, medial talar trochlea, lateral talar trochlea, lateral talar surface, tibial malleolus, medial tibial pla-fond, lateral tibial plafond, and fibular malleolus. Findings at flat-panel CT and MDCT arthrography were compared with macroscopic assessments in 80 cartilage areas. RESULTS: For the detection of cartilage lesions, flat-panel CT showed a sensitivity of 80%, specificity of 98%, and accuracy of 94%, and MDCT arthrography showed a sensitivity of 55%, specificity of 98%, and accuracy of 88%. Flat-panel CT and MDCT arthrography showed almost perfect (κ = 0.83) and substantial (κ = 0.65) agreement, respectively, with anatomic examination. Radiation dose was significantly lower for flat-panel CT (mean, 2.1 mGy; range, 1.1-3.0 mGy) than for MDCT (mean, 47.2 mGy; range, 39.3-53.8 mGy) (p < 0.01). CONCLUSION: Flat-panel CT arthrography is accurate for detecting cartilage defects in the ankle joint and is an alternative to MDCT arthrography that may have better diagnostic performance and may permit the use of a lower radiation dose.

Anterior shoulder instability: the role of advanced shoulder imaging in preoperative planning.

Despite advances in the understanding of anterior shoulder instability, recurrence rates after arthroscopic and open surgery have been reported to be as high as 30%. A successful operative outcome for patients with anterior shoulder instability requires the surgeon to perform a complete preoperative evaluation based on a thorough physical examination and advanced imaging techniques. In addition to the Bankart lesion, the treating surgeon must be aware of other copathologies, such as bony lesions of the glenoid or humeral head, humeral avulsion of the glenohumeral ligament, and articular cartilage defects that can occur in concert with capsular pathology and may necessitate a change in surgical strategy. This article focuses specifically on the osseous, labroligamentous, cartilage, and rotator cuff lesions demonstrated on preoperative imaging that are important to recognize in the preoperative work-up to optimize surgical outcomes for anterior instability.

Splenic sarcoidosis mimicking neoplastic disease.

Sarcoidosis is a multisystem granulomatous disease of unknown cause that commonly involves the spleen. Sarcoid can produce either homogeneous splenomegaly or multiple splenic nodules. Although other organ system involvement usually occurs, this is not invariable. Herein, we report on the clinical, histological, and radiological features-including sonography and MRI-of an isolated splenic sarcoidosis that mimicked neoplastic disease in a 37-year-old female. Knowledge of this atypical sonographic presentation may prevent unnecessary splenectomy.

Rotation in total knee arthroplasty: no difference between patient-specific and conventional instrumentation.

PURPOSE: It was our hypothesis that patient-specific instrumentation (PSI) can improve the accuracy of the rotational alignment in TKA based on the concept of the system and on the potential to clearly identify pre-operatively during planning the classical anatomical landmarks that serve as references to set-up the rotation both for the femur and tibia. MATERIALS AND METHODS: In this prospective comparative randomized study, 40 patients (20 in each group) operated in our institution between September 2012 and January 2013 by the 2 senior authors were included. Randomization of patients into one of the two groups was done by the Hospital Informatics Department with the use of a systematic sampling method. All patients received the same cemented high-flex mobile bearing TKA. In the PSI group, implant position was compared to the planed position using previously validated dedicated software. The position of the implants (frontal and sagittal) was compared in the 2 groups on standard X-rays, and the rotational position was analysed on post-operative CT-scan. RESULTS: 90 % of the patients add <2° or mm of difference between the planned position of the implants and the obtained position, except for the tibial rotation where the variations were much higher. Mean HKA was 179° (171-185) in the PSI group with 4 outliers (2 varus: 171° and 172°:184° and 185°) and 178.3° with 2 outliers (171° and 176°) in the control group. No difference was observed between the two groups concerning the frontal and sagittal position of the implants on the ML and AP X-rays. No significant difference of femoral rotation was observed between the two groups with a mean of 0.4° in the PSI group and 0.2° in the control group (p: n.s). Mean tibial rotation was 8° of internal rotation in the PSI group and 15° of internal rotation in the standard group (p: n.s). CONCLUSION: Based on our results, we were unable to confirm our hypothesis as PSI cannot improve rotation in TKA. More work needs to be done to more clearly define the place of PSI in TKA, to keep on improving the accuracy of the system and to better define the individual targets in TKA in terms of frontal, sagittal and rotational positioning of the implant for each patient. LEVEL OF EVIDENCE: Prospective comparative randomized study, Level II.