Point of care ultrasound combined with CTS-6 to diagnose idiopathic carpal tunnel syndrome.

BACKGROUND: This study aimed to demonstrate the effectiveness of our new diagnostic chart using point of care ultrasound combined with CTS-6 for diagnosing idiopathic carpal tunnel syndrome. METHODS: We conducted a retrospective analysis of the data of patients who visited our department and received point of care ultrasound combined with CTS-6 from 2020 to 2023. Data regarding age, sex, initial and final diagnosis, cross-sectional area of the median nerve, CTS-6 score, and electrodiagnostic severity were obtained and statistically analyzed. RESULTS: Of the 177 wrists included in our study, 138 (78 %) were diagnosed with carpal tunnel syndrome, while 39 (22 %) were not (non-carpal tunnel syndrome). With our diagnostic method, 127 wrists (72 %) were diagnosed initially with carpal tunnel syndrome, 23 wrists (13 %) with non-carpal tunnel syndrome, and the rest 27 wrists (15 %) as borderline. Our initial diagnoses of carpal tunnel syndrome and non-carpal tunnel syndrome were maintained in all cases except for two. Cross-sectional area, CTS-6 score, and electrodiagnostic severity showed a positive correlation. A post hoc analysis showed that the new scoring system (CTS-6 score + 2 × cross-sectional area) with a cutoff value of 31.25 points showed a sensitivity as high as 95 % and a specificity of 100 %. CONCLUSIONS: Our findings suggest that most suspected idiopathic carpal tunnel syndrome cases can be diagnosed correctly using the diagnostic chart. Although additional tools, including electrodiagnostic studies, may be needed for borderline cases, the use of point of care ultrasound combined with CTS-6 may be a recommendable first-line confirmatory test because point of care ultrasound and CTS-6 could be complementary tools, and this chart may be especially beneficial for atypical or outlier cases. LEVEL OF EVIDENCE: Diagnostic III.

Webplasty using an external fixator for complex syndactyly caused by Apert syndrome.

BACKGROUND: Webplasty can be conducted for complex syndactyly caused by Apert syndrome (also referred to as Apert hand) by extending the soft tissue in the lateral direction using an external fixator. This study aimed to verify the usefulness of webplasty without skin grafting. METHODS: Webplasty with lateral extension was conducted at a single institution from 2015 to 2023. The patients were four children with Apert hand aged 1-3 years. A custom-made small external fixator was used for all of the soft tissue extension. RESULTS: Webplasty without skin grafting was completed by the time all five patients were 5-6 years of age. CONCLUSION: Webplasty without skin grafting was possible with lateral extension of the soft tissue using a simple external fixator.

Excision of the hook of hamate in athletes using the carpal tunnel approach.

BACKGROUND: Hook of the hamate fractures can be managed conservatively or fixed using a screw, but excision is recommended for prompt return to activities. Although various approaches have been described, there is no gold standard. Herein, the authors have described their clinical experiences in excising the hook of the hamate using the carpal tunnel approach, in athletes. METHODS: A total of 36 athletes underwent excision of the hamate hook using the carpal tunnel approach. The mean age of the patients was 23 years, and most of them were baseball players (n = 31). RESULTS: The mean operation time was 33 min. None of the patients presented with any complications aside from transient pillar pain in five cases. All of them returned to their sports activities within an average of 27 days. CONCLUSIONS: In our study, excision of the hook of the hamate was performed safely via the carpal tunnel. The carpal tunnel approach reportedly provides superior benefits over other approaches.

Nonunion of the so-called acromion: a systematic review with consideration of the terminology.

INTRODUCTION: There is no widely accepted standard for the classification and treatment of traumatic acromion/scapular spine fracture nonunion due to the scarcity of this condition and the confusion of terminology. MATERIALS AND METHODS: PubMed and Scopus were searched using "scapular fracture" and "acromion fracture" or "scapular spine fracture" as search terms. The inclusion criteria were English full-text articles concerning acromion/scapular spine fracture nonunion that described patient characteristics and presented appropriate images. The exclusion criteria were cases without appropriate images. Citation tracking was conducted to find additional articles and notable full-text articles written in other languages. Fractures were classified using our newly proposed classification system. RESULTS: Twenty-nine patients (19 men, 10 women) with 29 nonunions were identified. There were four type I, 15 type II, and 10 type III fracture nonunions. Only 11 fractures were isolated. The mean period from initial injury to final diagnosis was 35.2 ± 73.2 months (range 3-360 months) (n = 25). The most frequent cause of delayed diagnosis was conservative treatment for fracture in 11 patients, followed by oversight by the physician in 8. The most common reason for seeking medical advice was shoulder pain. Six patients received conservative therapy, and 23 received operative treatment. Fixation materials included various plates in 15 patients, and tension band wiring in 5. Bone grafting was performed in 16 patients (73%, 16/22). Of the 19 surgically treated patients with adequate follow-up, the outcome was rated excellent in 79%. CONCLUSIONS: Isolated acromion/scapular spine fracture nonunion is rare. Fracture type II and III, arising in the anatomical scapular spine, accounted for 86% of the fractures. Computed tomography is required to prevent fracture oversight. Surgical therapy produces good stable results. However, it is important to select the appropriate surgical fixation method and material after considering the anatomical characteristics of the fracture and stress on the fractured portion. LEVEL OF EVIDENCE: V.

Aging Aggravates the Progression of Muscle Degeneration After Rotator Cuff Tears in Mice.

PURPOSE: The purpose of this study was to evaluate the impact of aging on muscle degeneration after rotator cuff tear (RCT) in mice. METHODS: Young (12-week-old) and aged (50-to-60-week-old) female C57BL/6 mice were used (n = 29 for each group). The rotator cuff was transected, and the proximal humerus was removed to induce degeneration of the rotator cuff muscles. The mice were euthanized 4 and 12 weeks after the procedure (referred to as RCT-4wk mice and RCT-12wk mice, respectively) and compared with the sham-treated mice. The supraspinatus muscles were collected for histology, Western blot analysis, and gene expression analyses. RESULTS: There was a significant increase in fat tissue in aged RCT-4wk mice (P = .001) and aged RCT-12wk mice (P < .001) compared with sham-treated aged mice, and aged RCT-12wk mice had a significantly increased fat area ratio compared with aged RCT-4wk mice (P < .001). The fat area was significantly larger in both the aged RCT-4wk (P = .002) and RCT-12wk mice (P < .001) than in the corresponding young mice. Muscular fibrosis was significantly increased in aged RCT-12wk mice compared with aged sham-treated mice (P = .005) and young RCT-12wk mice (P = .016). There were also significant increases in the expression of perilipin and transcripts of adipogenic and fibrogenic differentiation markers in aged RCT mice compared with young RCT mice. CONCLUSION: The present results show that aging is critically involved in the pathology of muscular fatty infiltration and fibrosis after RCT, and muscular degeneration progresses over time in aged mice. CLINICAL RELEVANCE: Aging promotes the progression of muscle degeneration in a mouse RCT model. Furthermore, this study shows that muscle degeneration occurs in aged mice even without denervation and that the model described in the present study is a useful tool for studying the pathology of muscle degeneration.

Total elbow arthroplasty using an augmented reality-assisted surgical technique.

BACKGROUND: Precision placement of implants in total elbow arthroplasty (TEA) using conventional surgical techniques can be difficult and riddled with errors. Modern technologies such as augmented reality (AR) and 3-dimensional (3D) printing have already found useful applications in many fields of medicine. We proposed a cutting-edge surgical technique, augmented reality total elbow arthroplasty (ARTEA), that uses AR and 3D printing to provide 3D information for intuitive preoperative planning. The purpose of this study was to evaluate the accuracy of humeral and ulnar component placement using ARTEA. METHODS: Twelve upper extremities from human frozen cadavers were used for experiments performed in this study. We scanned the extremities via computed tomography prior to performing TEA to plan placement sites using computer simulations. The ARTEA technique was used to perform TEA surgery on 6 of the extremities, whereas conventional (non-ARTEA) techniques were used on the other 6 extremities. Computed tomography scanning was repeated after TEA completion, and the error between the planned and actual placements of humeral and ulnar components was calculated and compared. RESULTS: For humeral component placement, the mean positional error ± standard deviation of ARTEA vs. non-ARTEA was 1.4° ± 0.6° vs. 4.4° ± 0.9° in total rotation (P = .002) and 1.5 ± 0.6 mm vs. 8.6 ± 1.3 mm in total translation (P = .002). For ulnar component placement, the mean positional error ± standard deviation of ARTEA vs. non-ARTEA was 5.5° ± 3.1° vs. 19.5° ± 9.8° in total rotation (P = .004) and 1.5 ± 0.4 mm vs. 6.9 ± 1.6 mm in total translation (P = .002). Both rotational accuracy and translational accuracy were greater for joint components replaced using the ARTEA technique compared with the non-ARTEA technique (P < .05). CONCLUSION: Compared with conventional surgical techniques, ARTEA had greater accuracy in prosthetic implant placement when used to perform TEA.

Three-Dimensional Quantitative Evaluation of the Scapular Skin Marker Movements in the Upright Posture.

Motion capture systems using skin markers are widely used to evaluate scapular kinematics. However, soft-tissue artifact (STA) is a major limitation, and there is insufficient knowledge of the marker movements from the original locations. This study explores a scapular STA, including marker movements with shoulder elevation using upright computed tomography (CT). Ten healthy males (twenty shoulders in total) had markers attached to scapular bony landmarks and underwent upright CT in the reference and elevated positions. Marker movements were calculated and compared between markers. The bone-based and marker-based scapulothoracic rotation angles were also compared in both positions. The median marker movement distances were 30.4 mm for the acromial angle, 53.1 mm for the root of the scapular spine, and 70.0 mm for the inferior angle. Marker movements were significantly smaller on the superolateral aspect of the scapula, and superior movement was largest in the directional movement. Scapulothoracic rotation angles were significantly smaller in the marker-based rotation angles than in the bone-based rotation angles of the elevated position. We noted that the markers especially did not track the inferior movement of the scapular motion with shoulder elevation, resulting in an underestimation of the marker-based rotation angles.

Change of wrist motion before and after fixation of the distal radioulnar joint and resection of the distal ulna in a cadaveric model.

OBJECTIVE: Recent study suggests the distal radioulnar joint (DRUJ) plays a role in flexion and extension of the wrist. We examined the range of motion (ROM) of the wrist before and after DRUJ fixation and distal ulnar resection in a cadaveric model. METHODS: Twenty fresh cadaveric human wrists were transected and treated with two sequential interventions: (a) DRUJ fixation, and (b) distal ulnar resection. The angle of maximum flexion and extension of the wrist was measured before and after the procedures. Maximum force to the wrist was determined before the procedures using a digital pressure monitor. RESULTS: The mean maximum wrist flexion ROM was 84.2° before the procedures. The ROM decreased to 82.5° after DRUJ fixation, and significantly increased to 88.2° after subsequent resection of the distal ulna. The mean maximum wrist extension ROM before the procedures was 73.5°. The ROM decreased to 71.6° after DRUJ fixation, and significantly increased to 77.1° after subsequent resection of the distal ulna. CONCLUSIONS: Motion of the wrist is affected by DRUJ. This study suggests that the DRUJ might contribute to the ROM in flexion and extension of the wrist.

Differences of tensile strength in knot tying technique between orthopaedic surgical instructors and trainees.

BACKGROUND: Knot tying technique is an extremely important basic skill for all surgeons. Clinically, knot slippage or suture breakage will lead to wound complications. Although some previous studies described the knot-tying technique of medical students or trainees, little information had been reported on the knot-tying technique of instructors. The objective of the preset study was to assess surgeons' manual knot tying techniques and to investigate the differences of tensile strength in knot tying technique between surgical instructors and trainees. METHODS: A total of 48 orthopaedic surgeons (postgraduate year: PGY 2-18) participated. Surgeons were requested to tie surgical knots manually using same suture material. They were divided into two groups based on each career; instructors and trainees. Although four open conventional knots with four throws were chosen and done with self-selected methods, knot tying practice to have the appropriate square knots was done as education only for trainees before the actual trial. The knots were placed over a 30 cm long custom made smooth polished surface with two cylindrical rods. All knots were tested for tensile strength using a tensiometer. The surgical loops were loaded until the knot slipped or the suture broke. The tensile strength of each individual knot was defined as the force (N) required to result in knot failure. Simultaneously, knot failure was evaluated based on knot slippage or suture rupture. In terms of tensile strength or knot failure, statistical comparison was performed between groups using two-tailed Mann-Whitney U test or Fisher exact probability test, respectively. RESULTS: Twenty-four instructors (PGY6-PGY18) and 24 trainees (PGY2-PGY5) were enrolled. Tensile strength was significantly greater in trainees (83.0 ± 27.7 N) than in instructors (49.9 ± 34.4 N, P = 0.0246). The ratio of slippage was significantly larger in instructors than in trainees (P < 0.001). Knot slippage (31.8 ± 17.7 N) was significantly worse than suture rupture (89.9 ± 22.2 N, P < 0.001) in tensile strength. CONCLUSIONS: Mean tensile strength of knots done by trainees after practice was judged to be greater than that done by instructors in the present study. Clinically, knot slippage can lead to wound dehiscence, compared to suture rupture.

Risk Factors Contributing to Early Implant Fracture in Silicone Metacarpophalangeal Joint Arthroplasty for Patients With Rheumatoid Arthritis.

PURPOSE: To identify the risk factors associated with early implant fracture of silicone metacarpophalangeal (MCP) joint arthroplasty using the volar hinge silicone implant for patients with rheumatoid arthritis. METHODS: We retrospectively reviewed 113 fingers of 31 hands that underwent MCP joint arthroplasty between 2008 and 2014, with a minimum follow-up of 3 years,. An implant fracture within 3 years after surgery was regarded as an early implant fracture. Patient records were reviewed for potential risk factors of age, affected fingers, ulnar drift angle, and range of motion of the MCP joint before surgery and 1 year after surgery. Candidate risk factors were compared at the level of the digit and at the patient level. RESULTS: With fracture of the implants as the end point, Kaplan-Meier estimated survival rate was 74.3% at 3 years and 67.9% at 5 years. Early implant fracture was detected in 29 fingers. Bivariate analyses showed significant associations between early implant fracture and MCP joint arc of motion before surgery, MCP joint flexion range 1 year after surgery, and MCP joint arc of motion 1 year after surgery. Multiple logistic regression analysis showed that increased MCP joint flexion range 1 year after surgery was an independent risk factor for early implant fracture. CONCLUSIONS: Increasing MCP joint flexion range was associated with increased fractures of the implants. We propose that the MCP joint flexion range should be restricted to less than 60° in postoperative rehabilitation; it is necessary to educate the patient to permanently avoid excessive flexion of the MCP joint. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Risk factors for failure of reduction of anterior glenohumeral dislocation without sedation.

BACKGROUND: Although anterior glenohumeral dislocations are common, the reduction procedure is often difficult, requiring sedation or anesthesia. To date, the risk factors for reduction failure without sedation have not been fully investigated. This study aimed to clarify the predictive factors that render the reduction of anterior glenohumeral dislocation without sedation difficult by use of multivariate analyses. METHODS: We retrospectively reviewed 156 patients who underwent attempted reduction of anterior glenohumeral dislocation between 2006 and 2019. Patients were included based on the following criteria: traumatic dislocation, undergoing attempted reduction using the traction-countertraction method, and acute dislocation in which reduction was attempted within 2 days of the injury. The dependent variable was set as an irreducible glenohumeral dislocation without sedation, which was defined as a reduction failure in this study. Explanatory variables included age, sex, side of injury, recurrent dislocation, axillary nerve injury, time from dislocation to attempted reduction, greater tuberosity fracture, humeral neck fracture, glenoid rim fracture, and glenohumeral osteoarthritis. We evaluated these outcomes from radiographs and clinical notes. Univariate and multivariate analyses were performed. Baseline variables, which were observed to be significant in the univariate analysis, were included in multivariate models, which used logistic regression to identify independent predictors of reduction failure. RESULTS: Of the 156 patients, 25 (16.0%) experienced reduction failure. Multivariate analyses showed that older age (≥55 years) (odds ratio [OR], 3.4; 95% confidence interval [CI], 1.1-10.4; P = .036), greater tuberosity fractures (OR, 3.6; 95% CI, 1.1-12.2; P = .033), and glenoid rim fractures (OR, 11.5; 95% CI, 1.5-87.7; P = .018) were risk factors for reduction failure. CONCLUSIONS: Our results demonstrated that multiple factors were associated with unsuccessful reduction of anterior glenohumeral dislocation without sedation. In elderly patients or patients with concurrent greater tuberosity fractures and glenoid rim fractures, reduction failure could occur in the absence of sedation; thus, the administration of sedatives or anesthesia should be considered.

Motion of the distal radioulnar joint in extension and flexion of the wrist using axial CT imaging of healthy volunteers.

BACKGROUND: The midcarpal joint and the radiocarpal joint contribute to the extension and flexion of the wrist. Little is known about the contribution of the distal radioulnar joint (DRUJ) to the extension and flexion of the wrist. This study evaluated the ulnar motion in extension and flexion of the wrist using computed tomography (CT) imaging. METHODS: A total of 30 wrists of healthy volunteers were enrolled. CT images of the axial sections of the DRUJ were obtained with 3 different positions of the wrist: 0° of extension (straight position), maximum active extension, and maximum active flexion. Each wrist motion was performed with 3 different forearm positions: neutral, pronation, and supination. Ulnar position at the DRUJ level was measured and ulnar position with the wrist in straight position was defined as baseline. The ulnar position was recorded as positive value when the position of the ulnar head was volar side and negative value when the position of the ulnar head was dorsal side. The difference from baseline in a position of maximum extension and flexion was evaluated. RESULTS: In forearm neutral position and pronation, a value of ulnar position in maximum wrist flexion is significantly negative compared to that in the wrist straight position: the ulnar head moved dorsally from the wrist straight position to wrist flexion. In forearm supination, a value of ulnar position in maximum wrist extension is significantly positive compared to that in the wrist straight position: the ulnar head moved to the volar side from the wrist straight position to wrist extension. CONCLUSIONS: The ulnar head moves during extension and flexion of the wrist. The direction of the ulnar motion was different according to the wrist and forearm position.

Nonunion of the coracoid process: a systematic review.

INTRODUCTION: Although the coracoid process seems to play an important anatomical role, there are few reports concerning fracture nonunion of the coracoid process (CN) and its disorders. Therefore, there is no widely accepted standard for the treatment of CN. MATERIALS AND METHODS: PubMed and Scopus were searched using "scapular fracture" and "coracoid fracture" as search terms. The inclusion criteria were English full-text articles concerning coracoid fracture, and articles that described patient characteristics and presented appropriate images. The exclusion criteria were descriptive cases, and cases without appropriate images. Citation tracking was conducted to find additional articles and notable full-text articles written in other languages. Fractures were classified using Ogawa's functional classification, with Eyres' anatomical classification used as a supplement when necessary. RESULTS: Twenty-nine patients (26 men, 3 women) with 30 CN were identified. Nine CN had a predisposing factor such as seizure disorder and renal osteodystrophy. The fracture types were 12 Ogawa type I and 18 type II. Concurrent shoulder girdle injuries at the time of initial trauma/accident were varied. There were six cases of double disruption and two of triple disruption of the superior shoulder suspensory complex (SSSC), all of which had Ogawa type I fracture. Only six CN were isolated. The most frequent cause of CN was oversight by the previous physician (n = 11), followed by conservative treatment (n = 7). Although 12 patients with 13 CN had symptoms attributable to CN, most of these symptoms were insignificant. Although the acromioclavicular dislocation or CN persisted in eight patients, these residual abnormalities did not significantly affect the outcomes. CONCLUSIONS: Physicians treating CN should recognize that CN itself is frequently asymptomatic, and a satisfactory outcome is achieved solely by treating the concurrent injuries, even if CN remains. When CN is suspected to produce symptoms, the physician must then determine the mechanism by which the symptoms are produced, and select a treatment strategy. LEVEL OF EVIDENCE: V.

Seasonal variation in the onset of acute calcific tendinitis of rotator cuff.

BACKGROUND: Calcific tendinitis of the rotator cuff is a disorder that causes acute onset of shoulder pain when spontaneous resorption of the calcification occurs. However, factors that trigger calcium resorption have not been clarified. The present study aimed to investigate the association between the onset of calcium resorption in calcific tendinitis and the season of onset. METHODS: We retrospectively reviewed 195 patients (female, 116; male, 79; mean age, 62.6 ± 14.2 years; median age, 62 [52, 73] years) diagnosed with the postcalcification stage of calcific tendinitis, which was defined as acute calcific tendinitis in this study, between 2006 and 2018. The onset date of acute calcific tendinitis for each patient was collected from clinical notes. We evaluated the incidence of acute calcific tendinitis in each season and month. Furthermore, we investigated the correlation between the incidence of acute calcific tendinitis and the mean monthly temperature or humidity levels for each year. RESULTS: The most common season of acute calcific tendinitis onset was summer (35.4%), followed by spring (24.6%), autumn (24.1%), and winter (15.9%) (P = 0.002). Monthly analyses showed the highest peak of onset was in July (15.4%) and the lowest peak was in February (3.1%) (P = 0.022). The incidence of acute calcific tendinitis had a weak association with mean monthly temperature (R2 = 0.066; P = 0.001) but was not associated with mean monthly humidity levels (R2 = 0.018; P = 0.099). CONCLUSIONS: This study provides new information on seasonal variation of acute calcific tendinitis onset. The results of this study indicated that the onset of calcium resorption occurs most frequently in the summer in Japan; however, the reasons for seasonal variation remain unclear, and further studies will be needed. LEVEL OF EVIDENCE: Level III.

Treatment of distal clavicle fractures using a Scorpion plate and influence of timing on surgical outcomes: a retrospective cohort study of 105 cases.

BACKGROUND: Plate fixation is an established method for treating unstable distal clavicle fractures. However, the appropriate timing of surgery for acute distal clavicle fractures remains unclear. The present study aimed to evaluate the clinical outcomes of osteosynthesis using a Scorpion plate and to assess the influence of surgery timing on the surgical outcomes for acute unstable distal clavicle fractures. METHODS: We retrospectively reviewed 105 patients who underwent fixation for acute unstable distal clavicle fractures (Neer type II and V) using the Scorpion plate between 2008 and 2018. Patients were divided into early (45 patients) and delayed (60 patients) treatment groups based on the timing of the surgical intervention (within or after 7 days). The outcomes were postoperative complications (nonunion, peri-implant fracture, plate loosening, plate-related pain, and stiffness). We evaluated the outcomes from X-ray radiographs and clinical notes. RESULTS: Among the 105 patients, nonunion, plate loosening, plate-related pain, and stiffness were observed in six patients (5.7%), four patients (3.8%), seven patients (6.7%), and one patient (1.0%), respectively. The nonunion rate was significantly higher in the delayed treatment group than that in the early treatment group (P = 0.036). Although the difference was not significant, plate loosening and stiffness were only observed in the delayed treatment group. CONCLUSION: Our results demonstrated that osteosynthesis using Scorpion plates achieved satisfactory surgical outcomes for unstable distal clavicle fractures. In addition, this study suggested that performing surgery within 6 days after injury is recommended to reduce postoperative complications.

Glenohumeral translation during active external rotation with the shoulder abducted in cases with glenohumeral instability: a 4-dimensional computed tomography analysis.

BACKGROUND: Although glenohumeral instability is common, the mechanism of instability remains unclear. The purpose of this study was to quantitatively evaluate humeral head translation during active external rotation with abduction in patients with glenohumeral instability by use of 4-dimensional computed tomography scans. METHODS: Ten patients with unilateral glenohumeral instability with a positive fulcrum test were prospectively included in this study. Sequential computed tomography of bilateral shoulders during active external rotation at 90° of shoulder abduction was performed for 6 seconds at 5 frames per second. The 3-dimensional positions of the humeral head center in the anteroposterior, superoinferior, and mediolateral directions were calculated at 0°, 20°, 40°, 60°, and maximum shoulder abduction-external rotation from the starting position. Translation of the humeral head center from the starting position was evaluated using Dunnett multiple-comparison tests, and the differences between the affected and intact shoulders were assessed using Wilcoxon signed rank tests. RESULTS: The humeral head center translated posteriorly, inferiorly, and medially during glenohumeral external rotation with the shoulder in the abducted position on the intact side. However, the affected humeral head showed significantly less posterior translation (P = .028), greater inferior translation (P = .047), and less medial translation (P = .037) than the contralateral side. CONCLUSIONS: This study indicated that dysfunction of the anterior band of the inferior glenohumeral ligament causes decreased posterior, increased inferior, and decreased medial translation of the humeral head during active shoulder abduction-external rotation.

The relationship between the morphological axis and the kinematic axis of the proximal radius.

PURPOSE: Surgical procedures for impaired forearm rotation such as for chronic radial head dislocation remain controversial. We hypothesized that the morphological axis of the proximal radius is important for stable forearm rotation, and we aimed to clarify the relationship between the morphological axis and the kinematic axis of the proximal radius using four-dimensional computed tomography (4DCT). METHODS: Ten healthy volunteers were enrolled. Four-dimensional CT of the dominant forearm during supination and pronation was obtained. The rotation axis of forearm rotation was calculated from all frames during supination and pronation. The principle axis of inertia, which represents the most stable rotation axis of a rigid body, was calculated for the proximal radius by extending its surface data incrementally by 1% from the proximal end. The angle between the kinematic rotation axis and the morphological rotation axis of each length was calculated. RESULTS: The rotation axis of the forearm was positioned on the radial head 0.0 mm radial and 0.4 mm posterior to the center of the radial head proximally and 2.0 mm radial and 1.2 mm volar to the fovea of the ulnar head distally. The principle axis at 15.9% of the length of the proximal radius coincided with the forearm rotation axis (kinematic axis). Individual differences were very small (SD 1.4%). CONCLUSION: Forearm rotation was based on the axis at 16% of the length of the proximal radius. This portion should be aligned in cases of severe morphological deformity of the radial head that cause "rattling motion" of the radial head after reduction procedures.

Evaluation of the Translation Distance of the Glenohumeral Joint and the Function of the Rotator Cuff on Its Translation: A Cadaveric Study.

PURPOSE: To evaluate the distance and position of humeral head translation during glenohumeral motion and to investigate the function of the rotator cuff in glenohumeral translation. METHODS: Using 9 cadavers, glenohumeral translation during passive pendulum motion was tracked by an optical motion capture system. Tension was applied to 5 compartments of the rotator cuff muscles, and 7 different conditions of rotator cuff dysfunction were sequentially simulated. Three-dimensional glenohumeral structure was reconstructed from the computed tomography images of the specimens, and the distance and position of glenohumeral translation were compared among the conditions. RESULTS: The average radius of glenohumeral translation was 10.6 ± 4.3 mm when static loading was applied to all rotator cuff muscles. The radius increased significantly in the models without traction force on the supraspinatus and total subscapularis tendons (P = .030). The position of the translation center did not change in the mediolateral direction (P = .587) and in the anteroposterior direction (P = .138), but it moved significantly superiorly in the models without supraspinatus and infraspinatus loading (P = .011) and in those without supraspinatus, infraspinatus, and teres minor loading (P < .001). CONCLUSIONS: The distance and position of humeral head translation during glenohumeral motion changed with rotator cuff deficiency. The present study indicated that the subscapularis plays an important role in maintaining the central position of the humeral head, and that the infraspinatus acts as a major depressor of the humeral head during shoulder motion. CLINICAL RELEVANCE: The results of this study suggest that extension of a tear into the subscapularis should be avoided to maintain the centering function of the glenohumeral joint in cases with rotator cuff tear.

Computed tomography-based 3-dimensional preoperative planning for unlinked total elbow arthroplasty.

HYPOTHESIS: Three-dimensional (3D) surgical planning for unlinked total elbow arthroplasty (TEA) would be helpful for estimation of the implant size and accurate placement of implants. METHODS: We included 28 patients who underwent TEA with an unlinked total elbow implant in this study. All patients underwent computed tomography scans of the elbow before surgery, and a 3D digital model of the elbow was reconstructed. After the appropriate size and position of the prosthesis were determined, 10 points around the bone tunnel (4 on the humerus and 6 on the ulna) were measured to plan the insertion of the humeral and ulnar stems. Two-dimensional planning was also performed using anteroposterior and lateral radiographs. Intraoperatively, the surgeon measured the planned parameters using a slide gauge to reproduce the 3D planned position of the stem insertion. RESULTS: The stem sizes were accurately estimated in 57% of patients for the humerus and 68% for the ulna with 2-dimensional planning and in 86% for the humerus and 96% for the ulna with 3D planning. The mean differences between the positions of the prostheses after surgery with reference to the planned positions were 0.8° of varus and 1.5° of flexion for the humeral component and 0.7° of varus and 2.9° of flexion for the ulnar component. We did not evaluate rotational positioning in this study. CONCLUSIONS: The 3D surgical planning allowed accurate estimation of the implant size and appropriate placement of implants. This method may contribute to a reduced incidence of complications and improved long-term outcomes from TEA.