Ulnar head replacement and sigmoid notch resurfacing arthroplasty with a lateral meniscal allograft: 'calamari procedure'

We report the outcomes of ulnar head replacement with concomitant resurfacing of the sigmoid notch with a lateral meniscal allograft that attempted to recreate the palmar and dorsal radioulnar ligaments in four patients. Patients' ranges of motion, grip strength, postoperative complications and radiographs were assessed. The mean follow-up was 20 (range 12-28) months. There was an increase in postoperative range of motion with an average increase in grip strength of 43% to the unaffected extremity. All patients experienced marked reduction in their postoperative pain. No patients reported symptoms of implant instability. Distal ulna implant arthroplasty with a lateral meniscal allograft gives favourable short-term outcomes.

LEVEL OF EVIDENCE

IV.

Extensor Carpi Ulnaris Instability Following Ulnar Shortening Osteotomy

Background Ulnar shortening osteotomy (USO) is a well-established procedure for the treatment of ulnar impaction syndrome. Although uncommon, the procedure can be associated with complications including nonunion, malunion, and hardware irritation. Case Description We present a 56-year-old woman who developed extensor carpi ulnaris (ECU) tendon instability following an USO. Literature Review The etiology of such a complication can be multifactorial. Clinical Relevance The recurrence of ulnar pain following an USO should raise the suspicion of possible ECU instability within the differential diagnosis.

Unplanned Readmissions Following Outpatient Hand and Elbow Surgery

BACKGROUND

Unplanned readmission following surgery is a quality metric that helps surgeons assess initiatives targeted at improving patient care. We utilized the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database to determine the rates, causes, and predictors of unplanned 30-day readmissions after outpatient elective hand and elbow surgery.

METHODS

The ACS-NSQIP database was queried using hand-and-elbow-specific Current Procedural Terminology (CPT) codes to retrospectively identify patients who had undergone outpatient hand or elbow surgery in 2012 and 2013. Patients who required an unplanned readmission to the hospital within 30 days were compared with those who were not readmitted. Preoperative patient characteristics, intraoperative variables, complications, and mortality were compared between the cohorts. Cox proportional hazard models were used to determine independent associations with 30-day unplanned readmission.

RESULTS

A total of 14,106 outpatient hand or elbow surgery procedures were identified between 2012 and 2013, and 169 (1.2%) of them were followed by an unplanned readmission. The leading causes of readmission included postoperative infections (19.5%), pain (4.7%), thromboembolic events (4.1%), and pulmonary complications (3.0%). The causes of approximately 1/3 of the readmissions were missing from the database, and these readmissions were likely unrelated to the principal procedure. Independent predictors of readmission included an age of 70 to 84 years (hazard ratio [HR] = 2.83, 95% confidence interval [CI] = 1.67 to 4.78), smoking (HR = 2.23, 95% CI = 1.57 to 3.18), a lower hematocrit (HR = 2.19, 95% CI = 1.38 to 3.46), renal dialysis (HR = 3.32, 95% CI = 1.60 to 6.91), and an elbow procedure (with or without a hand procedure) (HR = 2.19, 95% CI = 1.57 to 3.04).

CONCLUSIONS

The prevalence of unplanned readmission following outpatient hand and elbow surgery is low. Several modifiable factors, including preoperative smoking and anemia, are associated with unplanned readmission. These data may be helpful in developing quality-control initiatives to target unplanned readmissions following hand and elbow procedures.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Chondrocyte Attachment, Proliferation, and Differentiation on Three-Dimensional Polycaprolactone Fumarate Scaffolds

Current treatment options for cartilage injuries are limited. The goals of this study are to create a biodegradable polymer scaffold with the capabilities of sustaining chondrocyte growth and proliferation, enable cell-to-cell communication and tissue regeneration through large pores, and assess the biological augmentation of the scaffold capabilities using platelet lysate (PL). We synthesized biodegradable polycaprolactone fumarate (PCLF) scaffolds to allow cell-cell communication through large interconnected pores. Molds were printed using a three-dimensional printer and scaffolds synthesized through UV crosslinking. Culture medium included alpha modified Eagle's media with either 10% fetal bovine serum (FBS) or 5% PL, a mixture of platelet release products, after being seeded onto scaffolds through a dynamic bioreactor. Assays included cellular proliferation (MTS), toxicity and viability (live/dead immunostaining), differentiation (glycosaminoglycan [GAG], alkaline phosphatase [ALP], and total collagen), and immunostaining for chondrogenic markers collagen II and Sox 9 (with collagen I as a negative control). The large interconnected pores (500 and 750 μm) enable cell-to-cell communication and cellular infiltration into the scaffolds, as the cells remained viable and proliferated for 2 weeks. Chondrocytes cultured in PL showed increased rates of proliferation when compared with FBS. The chondrogenic markers GAG and total collagen contents increased over 2 weeks at each time point, whereas the osteogenic marker ALP did not significantly change. Immunostaining at 2 and 4 weeks for the expression of chondrogenic markers Collagen II and Sox 9 was increased when compared with control human fibroblasts. These results show that the PCLF polymer scaffold enables chondrocytes to attach, proliferate, and retain their chondrogenic phenotypes, demonstrating potential in chondrocyte engineering and cartilage regeneration.

Intra-articular dexamethasone to inhibit the development of post-traumatic osteoarthritis

Injury to the joint provokes a number of local pathophysiological changes, including synthesis of inflammatory cytokines, death of chondrocytes, breakdown of the extra-cellular matrix of cartilage, and reduced synthesis of matrix macromolecules. These processes combine to engender the subsequent development of post-traumatic osteoarthritis (PTOA). To prevent this from happening, it is necessary to inhibit these disparate responses to injury; given their heterogeneity, this is challenging. However, dexamethasone has the necessary pleiotropic properties required of a drug for this purpose. Using in vitro models, we have shown that low doses of dexamethasone sustain the synthesis of cartilage proteoglycans while inhibiting their breakdown after injurious compression in the presence or absence of inflammatory cytokines. Under these conditions, dexamethasone is non-toxic and maintains the viability of chondrocytes exposed chronically to such cytokines as interleukin (IL) -1, IL-6, and tumor necrosis factor-α. Moreover, the anti-inflammatory properties of dexamethasone have been appreciated for decades. In view of this information, we have initiated a pilot clinical study to determine whether a single, intra-articular injection of dexamethasone into the wrist shows promise in preventing PTOA after intra-articular fracture of the distal radius.

CLINICAL SIGNIFICANCE

Suppressing the various etiopathophysiological responses to injury in the joint is an attractive strategy for lowering the clinical burden of PTOA. The intra-articular administration of dexamethasone soon after injury offers a simple and inexpensive means of accomplishing this. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:406-411, 2017.

Capitate Chondroblastoma: A Case Report and Review of the Literature

Background: Chondroblastomas are benign tumors that typically occur in the epiphysis of long bones. Carpal bone chondroblastomas are very rare and are known to have less aggressive behavior with no evidence of recurrence reported. Methods: We present a case of a recurrent chondroblastoma in the capitate that was treated with repeat curettage, application of phenol, and bone grafting. Results: At 3 years post surgery, the patient is disease free with excellent functional return. Conclusion: Chondroblastomas are rare within the carpus. We present a review of the literature detailing their occurrence and treatment.

Long-Term Outcomes of Scaphoid Malunion

Background: The optimal treatment of patients with a scaphoid malunion remains controversial. The long-term outcomes of operative and nonoperative management have not been established. Methods: We conducted a retrospective review of the outcomes of all scaphoid malunions treated at single institution over a 30-year period. This included patients who underwent corrective osteotomy, salvage procedures (ie, dorsal cheilectomy, radial styloidectomy, and scaphoidectomy with midcarpal fusion), and those who refused operative intervention. The Mayo Wrist Score was determined at the time of surgical evaluation. Patient-Rated Wrist Evaluation (PRWE) and Disabilities of the Arm, Shoulder and Hand (QuickDASH) surveys were sent to all patients for long-term follow-up. Results: Seventeen patients had follow-up at a mean 21.4 years (range, 12-30 years). The mean initial lateral intrascaphoid angle was 58°. Of the 17 patients, 11 proceeded with surgery and 6 opted for nonoperative management. A corrective osteotomy was performed in 4 patients. Of the remaining 7 surgical patients, 5 patients underwent procedures such as cheilectomy and radial styloidectomy, whereas 2 patients had a scaphoidectomy with midcarpal fusion. The final mean PRWE and QuickDASH scores for corrective osteotomy, salvage procedures, and nonoperative treatment were 23 and 6, 18 and 10, and 33 and 22, respectively. Conclusion: Long-term outcomes were similar between operative and nonoperative management.

Current Quality Measurement Tools Are Insufficient to Assess Complications in Orthopedic Surgery

PURPOSE

The American College of Surgeons National Surgical Quality Improvement Project (ACS-NSQIP) is a clinically-derived, validated tool to track outcomes in surgery. The Agency for Healthcare Research and Quality Patient Safety Indicators (AHRQ-PSI) are a set of computer algorithms run on administrative data to identify adverse events. The purpose of this study is to compare complications following orthopedic surgery identified by ACS-NSQIP and AHRQ-PSI.

METHODS

Patients between 2010 and 2012 who underwent orthopedic procedures (arthroplasty, spine, trauma, foot and ankle, hand, and upper extremity) at our tertiary-care, academic institution were identified (n = 3,374). Identification of inpatient adverse events by AHRQ-PSI in the cohort was compared with 30-day events identified by ACS-NSQIP. Adverse events common to both AHRQ-PSI and ACS-NSQIP were infection, sepsis, venous thromboembolism, bleeding, respiratory failure, wound disruption, and renal failure. Concordance between AHRQ-PSI and ACS-NSQIP for identifying adverse events was examined.

RESULTS

A total of 729 adverse events (21.6%) were identified in the cohort using ACS-NSQIP methodology and 35 adverse events (1.0%) were found using AHRQ-PSI. Only 12 events were identified by both methodologies. The most common complication was bleeding in ACS-NSQIP (18.1%) and respiratory failure in AHRQ-PSI (0.53%). The overlap was highest for venous thromboembolic events. There was no overlap in adverse events for 5 of the 7 categories of adverse events.

CONCLUSIONS

A large discrepancy was observed between adverse events reported in ACS-NSQIP and AHRQ-PSI. A large percentage of clinically important adverse events identified in ACS-NSQIP were missed in AHRQ-PSI algorithms. The ability of AHRQ-PSI for detecting adverse events varied widely with ACS-NSQIP.

CLINICAL RELEVANCE

AHRQ-PSI algorithms currently are insufficient to assess the quality of orthopedic surgery.

Early Complications Following Osteosynthesis of Distal Radius Fractures: A Comparison of Geriatric and Nongeriatric Cohorts

BACKGROUND

Distal radius fractures (DRFs) are common geriatric fractures with the overall incidence expected to increase as the population continues to age. The purpose of this investigation was to compare the short-term complication rates in geriatric versus nongeriatric cohorts following osteosynthesis of DRFs.

METHODS

The American Board of Orthopaedic Surgery (ABOS) part II database was queried for adult DRF cases performed from 2007 to 2013. Current Procedural Terminology codes were used to identify cases treated via osteosynthesis. Patient demographic information and reported complication data were analyzed. Comparisons between geriatric (age ≥65 years) and nongeriatric (age <65 years) patients were performed.

RESULTS

From 2007 to 2013, a total of 9867 adult DRFs were treated via osteosynthesis by ABOS part II candidates. Geriatric patients comprised 28% of the study cohort. Mean age of the geriatric and nongeriatric cohorts was 74 ± 7 and 46 ± 13 years, respectively. There was a greater proportion of female patients (P < .001) in the geriatric cohort as compared with the nongeriatric cohort. The geriatric cohort demonstrated higher rates of anesthetic complications (P = .021), iatrogenic bone fracture (P = .021), implant failure (P = .031), loss of reduction (P = .001), unspecified medical complications (P = .007), and death (P = .017) than the nongeriatric cohort. The geriatric cohort also showed lower rates of nerve palsy (P = .028) when compared with the nongeriatric cohort, though no differences in rates of secondary surgery were noted between the two cohorts.

CONCLUSION

Increased rates of complications related to poor bone quality and poor health status may be expected among geriatric patients following osteosynthesis of DRFs. However, geriatric and nongeriatric patients have similarly low rates of secondary surgery. Future studies are needed to delineate the economic, functional, and societal impact of geriatric DRFs treated via osteosynthesis.

Proximal Scaphoid Pole Reconstruction Utilizing Ipsilateral Proximal Hamate Autograft

Background: Fractures of the proximal pole of the scaphoid can be difficult to heal because of its limited vascular supply. Furthermore, nonunion with avascular necrosis and secondary fragmentation makes surgical reconstruction a challenging procedure. Method: We describe a technique and report the outcome of a proximal hamate autograft to treat a proximal pole scaphoid nonunion with avascular necrosis. Results: At 3.5 years post reconstruction, the patient remains asymptomatic with union of his scaphoid reconstruction without any evidence of scapholunate instability. Conclusion: Proximal hamate autograft is a useful technique for addressing proximal pole scaphoid nonunions with avascular necrosis.

Risk Factors for Venous Thromboembolism following Thoracolumbar Surgery: Analysis of 43,777 Patients from the American College of Surgeons National Surgical Quality Improvement Program 2005 to 2012

Study Design Retrospective clinical study of a prospectively collected, national database. Objective Determine the 30-day incidence, timing, and risk factors for venous thromboembolism (VTE) following thoracolumbar spine surgery. Methods The American College of Surgeons National Surgical Quality Improvement Program Participant Use File identified 43,777 patients who underwent thoracolumbar surgery from 2005 to 2012. Multiple patient characteristics were identified. The incidence and timing (in days) of deep vein thrombosis (DVT) and pulmonary embolus (PE) were determined. Multivariable regression analysis was performed to identify significant risk factors. Results Of the 43,777 patients identified as having had thoracolumbar surgery, 202 cases of PE (0.5%) and 311 cases of DVT (0.7%) were identified. VTE rates were highest in patients undergoing corpectomy, with a 1.7% PE rate and a 3.8% DVT rate. Independent risk factors for VTE included length of stay (LOS) ≥ 6 days (odds ratio [OR] 4.07), disseminated cancer (OR 1.77), white blood cell count > 12 (OR 1.76), paraplegia (OR 1.75), albumin < 3 (OR 1.73), American Society of Anesthesiologists class 4 or greater (OR 1.54), body mass index > 40 (OR 1.49), and operative time > 193 minutes (OR 1.43). LOS < 3 days was protective (OR 0.427). Conclusions We report an overall 30-day PE rate of 0.5% and DVT rate of 0.7% following thoracolumbar spine surgery. Patients undergoing corpectomy were at highest risk for VTE. Multiple VTE risk factors were identified. Further studies are needed to develop algorithms to stratify VTE risk and direct prophylaxis accordingly.

The Role of Dynamic (4D) CT in the Detection of Scapholunate Ligament Injury

Background Scapholunate (SL) interosseus ligament injuries detected at an early stage could allow the surgeon to prevent progression through the spectrum of injury that leads to instability, and eventually osteoarthritis. We contend that early instability following injury can be detected by visualizing the relative motions and distances between the involved carpal bones (scaphoid and lunate) during wrist movement in vivo. The purpose of this study is to demonstrate the utility of dynamic CT (i.e., 4DCT) in diagnosing SL interosseus ligament injuries in two patients with clinical suspicion of SL interosseus ligament injury during flexion-extension (FE), radial-ulnar (RU) deviation, and dart thrower's (DT) motions. Case Description 4DCT images obtained from two individual cases were analyzed to assess the proximity between the scaphoid and lunate during wrist motion using standard image processing techniques. Proximity maps representing the distances between the scaphoid and lunate bones during each phase of wrist motion were determined. These maps provide insight into the severity of diastasis (large separation) and location of diastasis at the SL joint. The patients' proximity maps indicated dorsal diastasis and subtle uniform diastasis. Literature Review Complex musculoskeletal abnormalities, such as wrist joint instabilities, elude diagnosis during 2D fluoroscopy due to the 3D geometry of the anatomy and the inherent 3D nature of the bony kinematics. Even the most recent advances with MR arthrography lack good correlation with wrist arthroscopy. Wrist arthroscopy remains the gold standard for diagnosis to assess for intercarpal laxity. However, arthroscopy is an invasive procedure subjecting patients to the risk of infection, nerve injury, pain, and stiffness. Clinical Relevance 4DCT allows noninvasive characterization of where ligament injuries likely occur; this may allow for a more selective surgical treatment directed at the specific location of the tear.

Interpretation of Post-operative Distal Humerus Radiographs After Internal Fixation: Prediction of Later Loss of Fixation

PURPOSE

Stable fixation of distal humerus fracture fragments is necessary for adequate healing and maintenance of reduction. The purpose of this study was to measure the reliability and accuracy of interpretation of postoperative radiographs to predict which implants will loosen or break after operative treatment of bicolumnar distal humerus fractures. We also addressed agreement among surgeons regarding which fracture fixation will loosen or break and the influence of years in independent practice, location of practice, and so forth.

METHODS

A total of 232 orthopedic residents and surgeons from around the world evaluated 24 anteroposterior and lateral radiographs of distal humerus fractures on a Web-based platform to predict which implants would loosen or break. Agreement among observers was measured using the multi-rater kappa measure.

RESULTS

The sensitivity of prediction of failure of fixation of distal humerus fracture on radiographs was 63%, specificity was 53%, positive predictive value was 36%, the negative predictive value was 78%, and accuracy was 56%. There was fair interobserver agreement (κ = 0.27) regarding predictions of failure of fixation of distal humerus fracture on radiographs. Interobserver variability did not change when assessed for the various subgroups.

CONCLUSIONS

When experienced and skilled surgeons perform fixation of type C distal humerus fracture, the immediate postoperative radiograph is not predictive of fixation failure. Reoperation based on the probability of failure might not be advisable.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic III.

Long-Term Outcomes of Primary Repair of Chronic Thumb Ulnar Collateral Ligament Injuries

Background: The purpose of this study is to evaluate long-term outcomes of ligamentous repair rather than reconstruction for chronic thumb ulnar collateral ligament (UCL) injuries. Methods: Patients at least 15-years status-post repair of a chronic (greater than 6 weeks) UCL tear were contacted for clinical evaluation, radiographs, and postoperative outcome questionnaires, including the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire, visual analog scale (VAS) pain scale, and study-specific questions. Twelve of 21 (57%) living patients were available for long-term, greater than 15-year follow-up (average 24.5 years, range 16.9-35.6). Results: Eighty-eight percent of patients had some degree of osteoarthritis. Increased age at the time of injury and higher DASH scores were correlated with increased grades of the thumb metacarpophalangeal osteoarthritis. Delay to treatment and VAS pain scores had no correlation with radiographic findings. Conclusions: Repair of a chronic UCL injury with available local tissue appears to be a reasonable alternative to ligament reconstruction, resulting in durable long-term outcomes despite the majority of patients progressing to osteoarthritis.

Ligament Tissue Engineering Using a Novel Porous Polycaprolactone Fumarate Scaffold and Adipose Tissue-Derived Mesenchymal Stem Cells Grown in Platelet Lysate

PURPOSE

Surgical reconstruction of intra-articular ligament injuries is hampered by the poor regenerative potential of the tissue. We hypothesized that a novel composite polymer "neoligament" seeded with progenitor cells and growth factors would be effective in regenerating native ligamentous tissue.

METHODS

We synthesized a fumarate-derivative of polycaprolactone fumarate (PCLF) to create macro-porous scaffolds to allow cell-cell communication and nutrient flow. Clinical grade human adipose tissue-derived human mesenchymal stem cells (AMSCs) were cultured in 5% human platelet lysate (PL) and seeded on scaffolds using a dynamic bioreactor. Cell growth, viability, and differentiation were examined using metabolic assays and immunostaining for ligament-related markers (e.g., glycosaminoglycans [GAGs], alkaline phosphatase [ALP], collagens, and tenascin-C).

RESULTS

AMSCs seeded on three-dimensional (3D) PCLF scaffolds remain viable for at least 2 weeks with proliferating cells filling the pores. AMSC proliferation rates increased in PL compared to fetal bovine serum (FBS) (p < 0.05). Cells had a low baseline expression of ALP and GAG, but increased expression of total collagen when induced by the ligament and tenogenic growth factor fibroblast growth factor 2 (FGF-2), especially when cultured in the presence of PL (p < 0.01) instead of FBS (p < 0.05). FGF-2 and PL also significantly increased immunostaining of tenascin-C and collagen at 2 and 4 weeks compared with human fibroblasts.

SUMMARY

Our results demonstrate that AMSCs proliferate and eventually produce a collagen-rich extracellular matrix on porous PCLF scaffolds. This novel scaffold has potential in stem cell engineering and ligament regeneration.

Multiple Volar Carpometacarpal Dislocations: Case Report/Review of the Literature

Simultaneous volar dislocations of the second through fifth carpometacarpal joints are rare injuries, usually a result of high-energy trauma to the hand. The literature regarding this topic is sparse and consists primarily of case reports. We present a case associated with median nerve contusion that was treated with open reduction and pin fixation. The median nerve injury resolved without incident, and the pins were removed at 10 weeks without loss of reduction. Three years postoperatively, the patient was without pain and had excellent use of his hand without strength or motion deficit.

Predicting Fracture Risk for Enchondroma of the Hand

BACKGROUND

Enchondromas are benign cartilage tumors that can cause pathologic fractures involving the digits of the hand. The purpose of this study is to identify objective reproducible clinical criteria that are associated with fracture that can be used to guide clinical decision making.

METHODS

A total of 54 enchondroma cases involving the hand were retrospectively reviewed. Criteria examined included age, gender, the hand involved (left vs right), bone involved, the digit involved, and longitudinal percentage of the bone occupied by the lesion on anteroposterior (AP) radiographs.

RESULTS

There was a statistically significant difference between the fracture and nonfracture group in regard to age, the digit involved, bone involved, and the percentage of bone occupied by the lesion on AP radiographs.

CONCLUSION

This investigation provides evidence that patient age, the affected finger, the affected bone, and the percentage of the bone occupied by the pathologic lesion on AP radiographs can be used to predict pathologic fracture risk for enchondromas.

Phlpp1 facilitates post-traumatic osteoarthritis and is induced by inflammation and promoter demethylation in human osteoarthritis

OBJECTIVE

Osteoarthritis (OA) is the most common form of arthritis and a leading cause of disability. OA is characterized by articular chondrocyte deterioration, subchondral bone changes and debilitating pain. One strategy to promote cartilage regeneration and repair is to accelerate proliferation and matrix production of articular chondrocytes. We previously reported that the protein phosphatase Phlpp1 controls chondrocyte differentiation by regulating the activities of anabolic kinases. Here we examined the role of Phlpp1 in OA progression in a murine model. We also assessed PHLPP1 expression and promoter methylation.

DESIGN

Knee joints of WT and Phlpp1(-/-) mice were surgically destabilized by transection of the medial meniscal ligament (DMM). Mice were assessed for signs of OA progression via radiographic and histological analyses, and pain assessment for mechanical hypersensitivity using the von Frey assay. Methylation of the PHLPP1 promoter and PHLPP1 expression were evaluated in human articular cartilage and chondrocyte cell lines.

RESULTS

Following DMM surgeries, Phlpp1 deficient mice showed fewer signs of OA and cartilage degeneration. Mechanical allodynia associated with DMM surgeries was also attenuated in Phlpp1(-/-) mice. PHLPP1 was highly expressed in human articular cartilage from OA patients, but was undetectable in cartilage specimens from femoral neck fractures (FNFxs). Higher PHLPP1 levels correlated with less PHLPP1 promoter CpG methylation in cartilage from OA patients. Blocking cytosine methylation or treatment with inflammatory mediators enhanced PHLPP1 expression in human chondrocyte cell lines.

CONCLUSION

Phlpp1 deficiency protects against OA progression while CpG demethylation and inflammatory cytokines promote PHLPP1 expression.

Sonographic Visualization of Thenar Motor Branch of the Median Nerve: A Cadaveric Validation Study

BACKGROUND

The thenar motor branch (TMB) of the median nerve may be affected in carpal tunnel syndrome and can be injured during carpal tunnel surgery. Although ultrasound has been used to identify small nerves throughout the body, the sonographic evaluation of the TMB has not been investigated formally.

OBJECTIVE

To document the ability of ultrasound to visualize the TMB of the median nerve in an unembalmed cadaveric model.

DESIGN

Prospective laboratory investigation.

SETTING

Procedural skills laboratory at a tertiary medical center.

METHODS

On the basis of anatomical descriptions, dissection and clinical experience, a technique was developed to sonographically identify the presumed TMB of the median nerve at the distal carpal tunnel. A single, experienced examiner then identified the presumed TMB in 10 unembalmed, cadaveric upper limb specimens (4 right, 6 left) obtained from 9 donors (4 male, 5 female) ages 76-85 years with body mass indices of 18.2-29.5 kg/m² with both 12-3 MHZ and 16-7 MHz linear array transducers. The same examiner then injected 0.2-0.3 mL of diluted colored latex into and around the presumed TMB using direct ultrasound guidance. At a minimum of 24 hours postinjection, specimens were dissected under loupe magnification to determine the location of the latex injectate.

MAIN OUTCOME MEASURE

The location of latex injectate relative to the anatomically identified TMB.

RESULTS

A vertical, linear, hypoechogenic region was sonographically identified arising from the median nerve at the distal carpal tunnel in all 10 specimens and was hypothesized to represent the vertical segment of the TMB. Both transducers allowed identification of the TMB, although localization was subjectively facilitated by the higher frequency transducer. All 10 sonographically guided injections placed latex into and around the TMB of the median nerve, confirming that ultrasound had accurately identified the TMB.

CONCLUSIONS

Sonographic evaluation of the TMB of the median nerve is technically feasible and should be considered when clinically indicated. Further research and clinical experience is necessary to define the role of sonographic TMB imaging in the evaluation and management of patients with carpal tunnel syndrome.

LEVEL OF EVIDENCE

IV.