US for Traumatic Nerve Injury, Entrapment Neuropathy, and Imaging-guided Perineural Injection

US is commonly performed to help diagnose traumatic peripheral nerve injury and entrapment neuropathy, particularly with superficial nerves, where higher spatial resolution provides an advantage over MRI. Other advantages of US include dynamic evaluation, easy contralateral comparison, fewer implant contraindications, less artifact from ferromagnetic debris, and facile needle guidance for perineural injections. The authors review peripheral nerve US for traumatic peripheral nerve injury with an emphasis on injury grading and entrapment neuropathy and describe best-practice techniques for US-guided perineural injections while highlighting specific techniques and indications. Online supplemental material is available for this article. ^©RSNA, 2022.

Pre-treatment MRI of leukaemia and lymphoma in children: are there differences in marrow replacement patterns on T1-weighted images?

OBJECTIVES

To investigate the prevalence and distribution of specific marrow patterns on pre-treatment magnetic resonance imaging (MRI) examinations in children with leukaemia and lymphoma and with respect to the anatomic location.

MATERIALS AND METHODS

This retrospective IRB-approved and HIPAA-compliant study included children with leukaemia or lymphoma who underwent pre-treatment MRI examinations over 18 years (between 1 January 1995 and 31 August 2013). Two radiologists blinded to the clinical diagnosis reviewed each study to determine the presence or absence of abnormal marrow signal and, when present, sub-categorised the pattern into diffuse, patchy, or focal abnormal marrow. Chi-square and Fisher's exact tests were used to compare marrow patterns between leukaemia and lymphoma.

RESULTS

The study included 50 children (32 males and 18 females; mean age 9.5 ± 5.3 years) with 54 MRI examinations (27 leukaemia and 27 lymphoma) that included 26 spine and 28 non-spine studies. Marrow replacement was present on 43 (80%) studies, significantly more common with leukaemia than with lymphoma (p = 0.039). The diffuse replacement pattern was significantly more common with leukaemia when compared to lymphoma (p < 0.001) and the focal pattern was only observed with lymphoma. In the spine, the diffuse pattern was observed with lymphoma (3/14, 21%). All patients with leukaemia and MRI outside of the spine showed marrow involvement.

CONCLUSION

Marrow replacement is common on MRI from children with leukaemia and lymphoma. A diffuse pattern was significantly associated with leukaemia on studies outside of the spine and a focal pattern was only observed with lymphoma, independently of the anatomic location.

KEY POINTS

• Bone marrow replacement on pre-treatment MRI examinations in children with leukaemia and lymphoma was observed in 93% (25/27) and 67% (18/27), respectively. • Diffuse pattern of marrow replacement was significantly more common in leukaemia even though this pattern was also observed with lymphoma on the spine MRI studies. • Focal pattern of marrow replacement was present only with lymphoma and not with leukaemia regardless of the anatomic location.

Overuse Injuries of the Shoulder

This article discusses the most common and important overuse injuries of the shoulder with attention to MR imaging and ultrasound findings. Pathologic conditions occurring in athletes and nonathletes are included, with review of relevant anatomy, predisposing factors, and treatment considerations. Specific overuse injuries involving the rotator cuff, long head of the biceps tendon, and subacromial-subdeltoid bursa are reviewed. Impingement syndromes of the shoulder, Little Leaguer's shoulder, and stress-induced distal clavicular osteolysis are also discussed.

Orthopaedic Fixation Devices Used in Children: A Radiologist's Guide

Fractures are common in children with some requiring surgical reduction and fixation to maintain anatomical alignment. Although various surgical techniques and principles are shared between children and adults, certain unique considerations in children can influence the surgical approach and device selection. In particular, for skeletally immature children, it is of utmost importance to protect certain critical open growth plates because permanent injury can produce severe growth disturbances. The often robust healing response and potential limited patient compliance can also influence the treatment algorithm and decision making. Commonly encountered orthopaedic fixation devices, including screws, intramedullary devices, and plates, are reviewed with an emphasis on their mechanism and application in children. Additional miscellaneous devices that are commonly used to treat malalignment and guide bone growth including epiphysiodesis plates, proximal femur osteotomy plates, and spinal magnetic growing rods are also reviewed. The goal of this article is to provide a basic understanding of the principles and mechanisms of different types of pediatric orthopaedic devices and thereby improve the radiologist's diagnostic confidence and allow better anticipation of complications.

A biomechanical approach to interpreting magnetic resonance imaging of knee injuries

This article discusses common injury mechanisms and the subsequent constellation of magnetic resonance (MR) imaging findings in the knee following trauma in the context of instability, as distinguished by the degree of knee flexion and tibial rotation at the time of initial injury, in addition to the direction and magnitude of the responsible force vectors. Using 3-dimensional imaging, common injury mechanisms are illustrated and correlated with MR imaging findings of the resulting osteochondral, ligamentous, meniscal, and musculotendinous lesions. The most common classification and grading systems for these individual lesions and their subsequent treatment implications are discussed.

Magnetic resonance imaging and arthroscopic appearance of the menisci of the knee

The menisci are critical for normal function of the knee, providing shock absorption and load transmission that reduce stress on the articular cartilage. When torn, a meniscus may require surgery to restore function, reduce pain, and eliminate mechanical symptoms. Patterns of meniscal tears include longitudinal and bucket-handle, which are often reparable; and horizontal, radial, vertical flap, horizontal flap, and complex. Root tears are usually radial and occur in the posterior roots. When reviewing magnetic resonance images, one must be aware of normal variants and imaging pitfalls that may simulate pathology.

Percutaneous image-guided cryoablation of painful metastases involving bone: multicenter trial

BACKGROUND

This study sought to describe the results of a single-arm multicenter clinical trial using image-guided percutaneous cryoablation for the palliation of painful metastatic tumors involving bone.

METHODS

Over a 44-month period, 61 adult patients with 1 or 2 painful bone metastases with a score of 4 or more on a scale of 0 to 10 (≥4/10) worst pain in a 24-hour period who had failed or refused conventional treatment were treated with percutaneous image-guided cryoablation. Patient pain and quality of life was measured using the Brief Pain Inventory prior to treatment, 1 and 4 days after the procedure, weekly for 4 weeks, and every 2 weeks thereafter for a total of 6 months. Patient analgesic use was also recorded at these same follow-up intervals. Complications were monitored. Analysis of the primary endpoint was undertaken via paired comparison procedures.

RESULTS

A total of 69 treated tumors ranged in size from 1 to 11 cm. Prior to cryoablation, the mean score for worst pain in a 24-hour period was 7.1/10 with a range of 4/10 to 10/10. At 1, 4, 8, and 24 weeks after treatment, the mean score for worst pain in a 24-hour period decreased to 5.1/10 (P < .0001), 4.0/10 (P < .0001), 3.6/10 (P < .0001), and 1.4/10 (P < .0001), respectively. One of 61 (2%) patients had a major complication with osteomyelitis at the site of ablation.

CONCLUSIONS

Percutaneous cryoablation is a safe, effective, and durable method for palliation of pain due to metastatic disease involving bone.

Evaluation of the menisci of the knee joint using three-dimensional isotropic resolution fast spin-echo imaging: diagnostic performance in 250 patients with surgical correlation

OBJECTIVE

To compare the diagnostic performance of FSE-Cube, a three-dimensional isotropic resolution intermediate-weighted fast spin-echo sequence, with a routine magnetic resonance (MR) protocol at 3.0 T for detecting surgically confirmed meniscal tears of the knee joint in a large patient population.

METHODS

FSE-Cube was added to a routine MR protocol performed at 3.0 T on 250 patients who underwent subsequent knee arthroscopy. Three radiologists independently used FSE-Cube during one review and the routine MR protocol during a second review to detect medial and lateral meniscal tears. Using arthroscopy as the reference standard, the sensitivity and specificity of FSE-Cube and the routine MR protocol for detecting meniscal tears were determined for all readers combined. McNemar's tests were used to compare diagnostic performance between FSE-Cube and the routine MR protocol.

RESULTS

FSE-Cube and the routine MR protocol had similar sensitivity (95.5%/95.3% respectively, P = 0.94) and similar specificity (69.8%/74.0% respectively, P = 0.10) for detecting 156 medial meniscal tears. FSE-Cube had significantly lower sensitivity than the routine MR protocol (79.4%/85.0% respectively, P < 0.05) but similar specificity (83.9%/82.2% respectively, P = 0.37) for detecting 89 lateral mensical tears. For lateral meniscal tears, FSE-Cube had significantly lower sensitivity (P < 0.05) than the routine MR protocol for detecting 19 root tears but similar sensitivity (P = 0.17-1.00) for detecting all other tear locations and types.

CONCLUSION

FSE-Cube had diagnostic performance similar to a routine MR protocol for detecting meniscal tears except for a significantly lower sensitivity for detecting lateral meniscal tears, which was mainly attributed to decreased ability to identify lateral meniscus root tears.

Image-guided transnasal cryoablation of a recurrent nasal adenocarcinoma in a dog

An eight-year-old female spayed Airedale terrier with rapid recurrence of a nasal adenocarcinoma following image-guided intensity-modulated radiation therapy was treated with transnasal, image-guided cryotherapy. Ice ball size and location were monitored real-time with computed tomography-fluoroscopy to verify that the entire tumour was enveloped in ice. Serial computed tomography scans demonstrated reduction in and subsequent resolution of the primary tumour volume corresponding visually with the ice ball imaged during the ablation procedure. Re-imaging demonstrated focallysis of the cribriform plate following ablation that spontaneously resolved by 13 months. While mild chronic nasal discharge developed following cryoablation, no other clinical signs of local nasal neoplasia were present. Twenty-one months after nasal tumour cryoablation the dog was euthanased as a result of acute haemoabdomen. Image-guided cryotherapy may warrant further investigation for the management of focal residual or recurrent tumours in dogs, especially in regions where critical structures preclude surgical intervention.

Musculoskeletal mnemonics: differentiating features

Mnemonics are often used in musculoskeletal radiology to help radiologists remember long differential diagnoses. However, unless the specific appearance of each entity on a differential is also recalled, mnemonics become useless. This article presents 8 mnemonics with their corresponding differential diagnoses and distinguishing features. Bubbly lucent lesions of bone are recalled with the FEGNOMASHIC mnemonic, but when only lucent lesions of the diaphysis are included, a more appropriate mnemonic is FEMALE. The lucent lesions of bone differentials often can be narrowed based on specific characteristics of the lesion but radiographic findings elsewhere and clinical information often help. Osseous metastases may present as lucent or sclerotic lesions; when sclerotic, the differential is best remembered with the mnemonic 5 "BEES" Like Pollen. The mnemonic for Wormian bones is PORKCHOPS. The Wormian bones in most of these entities are indistinguishable, so one must rely on radiographic findings outside the skull for diagnosis. By contrast, differentiating causes of acro-osteolysis is often possible with findings seen only on the hand radiographs; the mnemonic for acro-osteolysis is RADSHIP. In skeletally immature patients with frayed metaphyses, the mnemonic is CHARMS. Although the appearance of the fraying is seldom diagnostic, findings in the adjacent portions of the long bones may be characteristic. FETISH is the mnemonic used to remember the entities for the differential diagnosis of vertebra plana. Age of the patient, clinical history, and findings in the adjacent spine often help to provide the specific diagnosis. Nearly all the entities on the differential diagnosis for distal clavicle erosion (mnemonic: SHIRT Pocket) are included in other differentials in this article.

Cartilage morphology at 3.0T: assessment of three-dimensional magnetic resonance imaging techniques

PURPOSE

To compare six new three-dimensional (3D) magnetic resonance (MR) methods for evaluating knee cartilage at 3.0T.

MATERIALS AND METHODS

We compared: fast-spin-echo cube (FSE-Cube), vastly undersampled isotropic projection reconstruction balanced steady-state free precession (VIPR-bSSFP), iterative decomposition of water and fat with echo asymmetry and least-squares estimation combined with spoiled gradient echo (IDEAL-SPGR) and gradient echo (IDEAL-GRASS), multiecho in steady-state acquisition (MENSA), and coherent oscillatory state acquisition for manipulation of image contrast (COSMIC). Five-minute sequences were performed twice on 10 healthy volunteers and once on five osteoarthritis (OA) patients. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured from the volunteers. Images of the five volunteers and the five OA patients were ranked on tissue contrast, articular surface clarity, reformat quality, and lesion conspicuity. FSE-Cube and VIPR-bSSFP were compared to IDEAL-SPGR for cartilage volume measurements.

RESULTS

FSE-Cube had top rankings for lesion conspicuity, overall SNR, and CNR (P < 0.02). VIPR-bSSFP had top rankings in tissue contrast and articular surface clarity. VIPR and FSE-Cube tied for best in reformatting ability. FSE-Cube and VIPR-bSSFP compared favorably to IDEAL-SPGR in accuracy and precision of cartilage volume measurements.

CONCLUSION

FSE-Cube and VIPR-bSSFP produce high image quality with accurate volume measurement of knee cartilage.

Knee joint: comprehensive assessment with 3D isotropic resolution fast spin-echo MR imaging--diagnostic performance compared with that of conventional MR imaging at 3.0 T

PURPOSE

To determine whether a three-dimensional isotropic resolution fast spin-echo sequence (FSE-Cube) has similar diagnostic performance as a routine magnetic resonance (MR) imaging protocol for evaluating the cartilage, ligaments, menisci, and osseous structures of the knee joint in symptomatic patients at 3.0 T.

MATERIALS AND METHODS

This prospective, HIPAA-compliant, institutional review board-approved study was performed with a waiver of informed consent. FSE-Cube was added to the routine 3.0-T MR imaging protocol performed in 100 symptomatic patients (54 male patients with a median age of 32 years and 46 female patients with a median age of 33 years) who subsequently underwent arthroscopic knee surgery. All MR imaging studies were independently reviewed twice by two musculoskeletal radiologists. During the first review, the routine MR imaging protocol was used to detect cartilage lesions, ligament tears, meniscal tears, and bone marrow edema lesions. During the second review, FSE-Cube with multiplanar reformations was used to detect these joint abnormalities. With arthroscopic results as the reference standard, the sensitivity and specificity of FSE-Cube and the routine MR imaging protocol in the detection of cartilage lesions, anterior cruciate ligament tears, and meniscal tears were calculated. Permutation tests were used to compare sensitivity and specificity values.

RESULTS

FSE-Cube had significantly higher sensitivity (P = .039) but significantly lower specificity (P = .003) than the routine MR imaging protocol for detecting cartilage lesions. There were no significant differences (P = .183-.999) in sensitivity and specificity between FSE-Cube and the routine MR imaging protocol in the detection of anterior cruciate ligament tears, medial meniscal tears, or lateral meniscal tears. FSE-Cube depicted 96.2% of medial collateral ligament tears, 100% of lateral collateral ligament tears, and 85.3% of bone marrow edema lesions identified on images obtained with the routine MR imaging protocol.

CONCLUSION

FSE-Cube has similar diagnostic performance as a routine MR imaging protocol for detecting cartilage lesions, cruciate ligament tears, collateral ligament tears, meniscal tears, and bone marrow edema lesions within the knee joint at 3.0 T.

Correlation of MRI findings with clinical findings of trochanteric pain syndrome

OBJECTIVE

Greater trochanter pain syndrome due to tendinopathy or bursitis is a common cause of hip pain. The previously reported magnetic resonance (MR) findings of trochanteric tendinopathy and bursitis are peritrochanteric fluid and abductor tendon abnormality. We have often noted peritrochanteric high T2 signal in patients without trochanteric symptoms. The purpose of this study was to determine whether the MR findings of peritrochanteric fluid or hip abductor tendon pathology correlate with trochanteric pain.

MATERIALS AND METHODS

We retrospectively reviewed 131 consecutive MR examinations of the pelvis (256 hips) for T2 peritrochanteric signal and abductor tendon abnormalities without knowledge of the clinical symptoms. Any T2 peritrochanteric abnormality was characterized by size as tiny, small, medium, or large; by morphology as feathery, crescentic, or round; and by location as bursal or intratendinous. The clinical symptoms of hip pain and trochanteric pain were compared to the MR findings on coronal, sagittal, and axial T2 sequences using chi-square or Fisher's exact test with significance assigned as p < 0.05.

RESULTS

Clinical symptoms of trochanteric pain syndrome were present in only 16 of the 256 hips. All 16 hips with trochanteric pain and 212 (88%) of 240 without trochanteric pain had peritrochanteric abnormalities (p = 0.15). Eighty-eight percent of hips with trochanteric symptoms had gluteus tendinopathy while 50% of those without symptoms had such findings (p = 0.004). Other than tendinopathy, there was no statistically significant difference between hips with or without trochanteric symptoms and the presence of peritrochanteric T2 abnormality, its size or shape, and the presence of gluteus medius or minimus partial thickness tears.

CONCLUSIONS

Patients with trochanteric pain syndrome always have peritrochanteric T2 abnormalities and are significantly more likely to have abductor tendinopathy on magnetic resonance imaging (MRI). However, although the absence of peritrochanteric T2 MR abnormalities makes trochanteric pain syndrome unlikely, detection of these abnormalities on MRI is a poor predictor of trochanteric pain syndrome as these findings are present in a high percentage of patients without trochanteric pain.

Musculoskeletal Radiology Curriculum for Radiology Residents

This article outlines a curriculum for resident education in musculoskeletal radiology that addresses the current requirements for assessment of the general competencies as set forth by the Accreditation Council for Graduate Medical Education.

Cervical spine injury severity score. Assessment of reliability

BACKGROUND

Systems for classifying cervical spine injury most commonly use mechanistic or morphologic terms and do not quantify the degree of stability. Along with neurologic function, stability is a major determinant of treatment and prognosis. The goal of our study was to investigate the reliability of a method of quantifying the stability of subaxial (C3-C7) cervical spine injuries.

METHODS

A quantitative system was developed in which an analog score of 0 to 5 points is assigned, on the basis of fracture displacement and severity of ligamentous injury, to each of four spinal columns (anterior, posterior, right pillar, and left pillar). The total possible score thus ranges from 0 to 20 points. Fifteen examiners assigned scores after reviewing the plain radiographs and computed tomography images of thirty-four consecutive patients with cervical spine injuries. The scores were then evaluated for interobserver and intraobserver reliability with use of intraclass correlation coefficients.

RESULTS

The mean intraobserver and interobserver intraclass correlation coefficients for the fifteen reviewers were 0.977 and 0.883, respectively. Association between the scores and clinical data was also excellent, as all patients who had a score of > or =7 points had surgery. Similarly, eleven of the fourteen patients with a score of > or =7 points had a neurologic deficit compared with only three of the twenty with a score of <7 points.

CONCLUSIONS

The Cervical Spine Injury Severity Score had excellent intraobserver and interobserver reliability. We believe that quantifying stability on the basis of fracture morphology will allow surgeons to better characterize these injuries and ultimately lead to the development of treatment algorithms that can be tested in clinical trials.

Intensity of signal contacting meniscal surface in recurrent tears on MR arthrography compared with that of contrast material

OBJECTIVE

Several previous studies reported that the signal contacting the meniscal surface in a recurrent tear on MR arthrography had intensity equal to that of intraarticular contrast material. Because we failed to diagnose recurrent tears using this criterion, we reviewed our knee MR arthrograms in patients who had prior meniscal surgery.

CONCLUSION

On knee MR arthrograms, the signal contacting the surface of a recurrent meniscal tear may be equal to or less than that of adjacent intraarticular gadolinium contrast material.

Imaging of wrist masses

The wrist is a complex structure with an extensive differential diagnosis for a presenting mass. However, the vast majority of hand and wrist masses are benign, and many of these have a distinctive radiographic appearance. In this article, the imaging characteristics of the most common entities are reviewed with particular attention to magnetic resonance appearance. The 3 most common hand and wrist lesions include ganglion cysts, giant cell tumors of the tendon sheath, and hemangiomas. Other common lesions that can be diagnosed radiographically include lipomas, neural sheath tumors, infection and inflammation, and variant soft-tissue or bony structures. The appearance of the fibrolipomatous hamartoma will also be demonstrated because this is a radiographically distinctive, though rare, lesion.

Epidural steroid injections

Epidural steroid injections have a significant role in the treatment of patients with low back, neck, and radicular pain. Although these procedures may not address the causative lesions, they often shorten the clinical course of the disease process, keep patients out of the hospital, and provide symptomatic relief that improves quality of life. These procedures are most accurately performed with fluoroscopic guidance and major complications are rare. Although support for cervical epidural steroid injection is less uniform than that for lumbar and caudal injections, a growing body of experience is beginning to support its efficacy and safety.

Selective nerve root blocks

Selective nerve root blocks are valuable diagnostic and therapeutic procedures in patients with radicular symptoms. Understanding the anatomy, benefits, and risks, as well as precise needle placement, are important factors in performing successful nerve root blocks. The techniques we describe come from our training and ongoing experience. There are other acceptable methods as well.

MR imaging of the postoperative meniscus of the knee

Surgery for tears of the menisci of the knee has evolved greatly over the last century and is now an extremely common procedure. Meniscal repair and conservative therapy are the preferred methods of treatment, but most symptomatic torn menisci do not meet the requirements for these options and necessitate partial meniscectomy. After surgery, patients often have recurrent pain and need additional diagnosis. Conventional magnetic resonance imaging (MRI) in the postoperative patient is very helpful at diagnosing extrameniscal pathology. It has lower sensitivity for detecting retears after partial meniscectomy, however, as it relies primarily on demonstration of fluid entering the meniscal retear on T2-weighted images. Similarly, conventional MRI is less accurate after meniscal repair, in which the repair site usually maintains altered signal for years. MR arthrography has higher sensitivity for detecting retears in menisci and is the procedure of choice in many situations.

Navigating the thoracic inlet

The thoracic inlet is often seen on the "edge of the film" at computed tomography (CT); consequently, lesions affecting this structure are easily overlooked. A vascular abnormality that may be overlooked is venous thrombosis. The CT appearance of jugular vein thrombosis varies with the age of the lesion: In the acute phase, there is often loss of soft-tissue planes surrounding an enlarged, peripherally enhancing thrombus. In the chronic phase, the jugular vein appears as a tubular, nonenhancing "mass" without loss of surrounding fat planes. Intrathoracic goiters typically manifest as well-defined, markedly enhanced inhomogeneous lesions that are continuous with the cervical thyroid gland. Thyroid adenomas are typically round or oval low-attenuating lesions that enhance after contrast material administration. Thyroid carcinomas may manifest as single or multiple, irregularly shaped low-attenuating areas with or without calcification. Primary tracheal malignancies may appear as smooth or irregular, sessile or pedunculated intraluminal filling defects. Tracheomalacia manifests as destruction of the tracheal walls with soft-tissue narrowing of the tracheal lumen, whereas esophageal abnormalities manifest as thickening of the esophageal wall, dilatation of the esophageal lumen, or both. Schwannomas manifest as well-circumscribed lesions with soft-tissue attenuation that enhance after contrast material administration. Neurofibromas tend to have lower attenuation than schwannomas. Lymphangiomas typically have a cystic appearance with near water attenuation. Familiarity with the normal anatomy of the thoracic inlet as well as the CT features of related abnormalities is critical for correct diagnosis and prompt treatment.

The rationale and a computer evaluation of a gamma irradiation sterilization dose determination method for medical devices using a substerilization incremental dose sterility test protocol

The experimental procedure described is designed to allow calculation of the radiation sterilization dose for medical devices to any desired standard of sterility assurance. The procedure makes use of the results of a series of sterility tests on device samples exposed to doses of radiation from 0.2 to 1.8 Mrad in 0.2 Mrad increments. From the sterility test data a 10(-2) sterility level dose is determined. A formula is described that allows a value called DS Mrad to be calculated. This is an estimate of the effective radiation resistance of the heterogeneous microbial population remaining in the tail portion of the inactivation curve at the 10(-2) dose and above. DS Mrad is used as a D10 value and is applied, in conjunction with the 10(-2) sterility level dose, to an extrapolation factor to estimate a sufficient radiation sterilization dose. A computer simulation of the substerilization process has been carried out. This has allowed an extensive evaluation of the procedure, and the sterilization dose obtained from calculation to be compared with the actual dose required. Good agreement was obtained with most microbial populations examined, but examples of both overdosing and underdosing were found with microbial populations containing a proportion of organisms displaying pronounced shoulder inactivation kinetics. The method allows the radiation sterilization dose to be derived from the natural resistance of the microbial population to gamma sterilization.

A biologic comparison of polyglactin 910 and polyglycolic acid synthetic absorbable sutures

Two synthetic absorbable sutures were implanted in rats for a comparative evaluation of breaking strength, tissue reaction and absorption. Polyglactin 910 suture was stronger than polyglycolic acid suture in both sizes tested and at all time periods from zero to 35 days. Both suture types elicited minimal tissure response. Based upon histologic examination, virtually all remnants of the polyglactin 910 were absorbed by 90 days, while considerable quantities of polyglycolic acid persisted at 120 days. The difference in absorption rates was a highly significant feature of the comparative biologic profiles of the two suture materials.