The effect of forearm rotation on the bone mineral density measurements of the distal radius.

INTRODUCTION: Forearm dual-energy X-ray absorptiometry (DXA) is often performed in clinics where central DXA is unavailable. Accurate bone mineral density (BMD) measurement is crucial for clinical assessment. Forearm rotation can affect BMD measurements, but this effect remains uncertain. Thus, we aimed to conduct a simulation study using CT images to clarify the effect of forearm rotation on BMD measurements. MATERIALS AND METHODS: Forearm CT images of 60 women were analyzed. BMD was measured at the total, ultra-distal (UD), mid-distal (MD), and distal 33% radius regions with the radius located at the neutral position using digitally reconstructed radiographs generated from CT images. Then, the rotation was altered from - 30° to 30° (supination set as positive) with a one-degree increment, and the percent BMD changes from the neutral position were quantified for all regions at each angle for each patient. RESULTS: The maximum mean BMD changes were 5.8%, 7.0%, 6.2%, and 7.2% for the total, UD, MD, and distal 33% radius regions, respectively. The analysis of the absolute values of the percent BMD changes from the neutral position showed that BMD changes of all patients remained within 2% when the rotation was between - 5° and 7° for the total region, between - 3° and 2° for the UD region, between - 4° and 3° for the MD region, and between - 3° and 1° for the distal 33% radius region. CONCLUSION: Subtle rotational changes affected the BMD measurement of each region. The results showed the importance of forearm positioning when measuring the distal radius BMD.

Neurotropin® accelerates peripheral nerve regeneration in a rat sciatic nerve crush injury model.

BACKGROUND: Peripheral nerve injuries are common and serious conditions. The effect of Neurotropin® (NTP), a nonprotein extract derived from the inflamed skin of rabbits inoculated with vaccinia virus, on peripheral nerve regeneration has not been fully elucidated. However, it has analgesic properties via the activation of descending pain inhibitory systems. Therefore, the current study aimed to determine the effects of NTP on peripheral nerve regeneration. METHODS: We examined axonal outgrowth of dorsal root ganglion (DRG) neurons using immunocytochemistry in vitro. In addition, nerve regeneration was evaluated functionally, electrophysiologically, and histologically in a rat sciatic nerve crush injury model in vivo. Furthermore, gene expression of neurotrophic factors in the injured sciatic nerves and DRGs was evaluated. RESULTS: In the dorsal root ganglion neurons in vitro, NTP promoted axonal outgrowth at a concentration of 10 mNU/mL. Moreover, the systemic administration of NTP contributed to the recovery of motor and sensory function at 2 weeks, and of sensory function, nerve conduction velocity, terminal latency, and axon-remyelination 4 weeks after sciatic nerve injury. In the gene expression assessment, insulin-like growth factor 1 and vascular endothelial growth factor expressions were increased in the injured sciatic nerve 2 days postoperatively. CONCLUSIONS: Therefore, NTP might be effective in not only treating chronic pain but also promoting peripheral nerve regeneration after injury.

Cubitus varus deformity following paediatric supracondylar humeral fracture remodelling predominantly in the sagittal direction: A three-dimensional analysis of eighty-six cases.

PURPOSE: Three-dimensional (3D) capacity for remodelling in cubitus varus deformity (CVD) after paediatric supracondylar humeral fractures (PSHFs) remains unelucidated. This study investigated remodelling patterns after PSHFs by examining 3D deformity distribution over time after injury. METHODS: Computed tomography (CT) data of 86 patients with CVD after PSHFs were analysed. The 3D deformity angles in the sagittal, coronal, and axial directions were assessed and correlated with the duration between the age at injury and CT evaluation. For the subgroup analysis, we performed the same correlation analysis in a younger (< 8 years old) and an older group (≥ 8 years old); we categorized the duration into early (< 2 years), middle (≥ 2 to < 5 years), and late periods (≥ 5 years) and compared the deformity angles of each direction among the three groups. RESULTS: Sagittal deformity showed a moderate correlation with the duration of deformity (r = -0.54; P < 0.001), while coronal and axial deformities showed a negligible correlation. Sagittal deformity showed moderate correlations with the duration in the younger group (r = -0.62; P < 0.001) and weak correlations in the older group (r = -0.37; P = 0.091). In the sagittal direction, the deformity angle in the early period was significantly larger than those in the mid and late periods (P < 0.001). However, there were no significant differences among the three groups in the coronal and axial directions. CONCLUSION: Sagittal deformities in CVDs are capable of remodelling, especially in the early period and at a younger age, whereas coronal and axial deformities are less likely to undergo remodelling.

Comparison of the Orientation Angles of Volar Locking Plate Distal Ulnar Locking Screw for Distal Radius Fractures.

PURPOSE: This study aimed to measure the angles between the screw and plate in 16 commercially available volar locking plates (VLPs) to determine the fixable intra-articular fragment size. METHODS: Ulnar orientation angles (axial plane) and elevation angles (sagittal plane) between the distal ulnar screw and plate were measured for 14 fixed-angle VLPs and 2 variable-angle VLPs. Each VLP was simulated by 2 surgeons to sit distally and ulnarly in 10 normal distal radius models. The distance between the screw and distal/ulnar end of the distal radius on both the volar and dorsal sides, designated as the longitudinal/lateral distance, was measured to identify the fixable size of the 2 intra-articular fragments: volar lunate fragment and dorsoulnar fragment. Relationships between the ulnar orientation angle and dorsal-side lateral length as well as the elevation angle and dorsal-side longitudinal distance were analyzed. RESULTS: The ulnar orientation and elevation angles ranged from 6.5° to 16.9° and -5.8° to 34.3°, respectively, for fixed-angle VLPs and -12.5° to 32.2° and 3.1° to 42.1°, respectively, for variable-angle VLPs. The minimal longitudinal distances on the volar side with the fixed- and variable-angle VLPs were 4.3-10.9 mm and 5.8-5.9 mm, respectively. On the dorsal side, the lateral distance negatively correlated with the ulnar orientation angle (R = -0.74), and the longitudinal distance negatively correlated with the elevation angle (R = -0.89). CONCLUSIONS: The Depuy Synthes variable-angle VLP provides an advantage for fixating small intra-articular fragments. For fixed-angle VLPs, the Mizuho VLP provides an advantage for fixating small volar lunate fragments. A narrow dorsoulnar fragment can be fixated using a plate with a large ulnar orientation angle, such as the Zimmer Biomet or Mizuho VLP. CLINICAL RELEVANCE: The ability of each individual commercially available plate to capture specific intra-articular fragments should be known.

A Quantitative Analysis of Subchondral Bone Density Around Osteochondritis Dissecans Lesions of the Capitellum.

PURPOSE: In capitellar osteochondritis dissecans (OCD), unstable lesions generally demonstrate signs of subchondral sclerosis. We postulate that OCD lesions have abnormal subchondral bone density. We aimed to quantify the subchondral bone thickness around OCD lesions using conventional computed tomography (CT) imaging. METHODS: This retrospective study included 15 patients with capitellar OCD (OCD group) and 12 patients with an unaffected radio-capitellar joint (control group). We constructed 3-dimensional humerus models using CT data and quantified the bone density with colored contour mapping to determine the subchondral bone thickness. We measured the thickness relative to the condylar height at the centroid and lateral, medial, superior, and inferior edge points of the OCD lesion, and compared the findings between the groups. We then correlated the CT measurements with the magnetic resonance imaging measurements. RESULTS: Subchondral bone thickness at the centroid and lateral, medial, superior, and inferior edges in the OCD group was significantly higher than that in the control group. Correlation analyses revealed that the magnetic resonance imaging measurements highly correlated with the CT subchondral bone measurements. CONCLUSIONS: We found that there is a zone of increased subchondral bone thickness around OCD lesions that should be considered during drilling, microfracture, or other reconstruction methods. We observed a high correlation with low errors between the measurements taken from conventional CT images and the measurements from magnetic resonance imaging, suggesting that both modalities are useful in clinical decision making. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic IV.

Comparing the locking screw direction of three locking plates for lateral clavicle fractures: a simulation study.

BACKGROUND: The locking plate is a useful treatment for lateral clavicle fractures, however, there are limits to the fragment size that can be fixed. The current study aimed to measure the screw angles of three locking plates for lateral clavicle fractures. In addition, to assess the number of screws that can be inserted in different fragment sizes, to elucidate the size limits for locking plate fixation. METHODS: The following three locking plates were analyzed: the distal clavicle plate [Acumed, LLC, Oregon, the USA], the LCP clavicle plate lateral extension [Depuy Synthes, LLC, PA, the USA], and the HAI clavicle plate [HOMS Engineering, Inc., Nagano, Japan]. We measured the angles between the most medial and lateral locking screws in the coronal plane and between the most anterior and posterior locking screws in the sagittal plane. A computer simulation was used to position the plates as laterally as possible in ten normal three-dimensional clavicle models. Lateral fragment sizes of 10, 15, 20, 25, and 30 mm were simulated in the acromioclavicular joint, and the number of screws that could be inserted in the lateral fragment was assessed. Subsequently, the area covered by the locking screws on the inferior surface of the clavicle was measured. RESULTS: The distal clavicle plate had relatively large screw angles (20° in the coronal plane and 32° in the sagittal plane). The LCP clavicle lateral extension had a large angle (38°) in the sagittal plane. However, the maximum angle of the HAI clavicle plate was 13° in either plane. The distal clavicle plate allowed most screws to be inserted in each size of bone fragment. For all locking plates, all screws could be inserted in 25 mm fragments. The screws of distal clavicle plate covered the largest area on the inferior surface of the clavicle. CONCLUSIONS: Screw angles and the numbers of screws that could be inserted in the lateral fragment differed among products. Other augmented fixation procedures should be considered for fractures with fragment sizes < 25 mm that cannot be fixed with a sufficient number of screws.

Utility of a 3-dimensionally printed color-coded bone model to visualize impinging osteophytes for arthroscopic débridement arthroplasty in elbow osteoarthritis.

BACKGROUND: The identification and precise removal of bony impingement lesions during arthroscopic débridement arthroplasty for elbow osteoarthritis require a high level of experience and surgical skill. We have developed a new technique to identify impinging osteophytes on a computer display by simulating elbow motion using the multiple positions of 3-dimensional (3D) elbow models created from computed tomography data. Moreover, an actual color-coded 3D model indicating the impinging osteophytes was created with a 3D printer and was used as an intraoperative reference tool. This study aimed to verify the efficacy of these new technologies in arthroscopic débridement for elbow osteoarthritis. METHODS: We retrospectively studied 16 patients treated with arthroscopic débridement for elbow osteoarthritis after a preoperative computer simulation. Patients who underwent surgery with only the preoperative simulation were assigned to group 1 (n = 8), whereas those on whom we operated using a color-coded 3D bone model created from the preoperative simulation were assigned to group 2 (n = 8). Elbow extension and flexion range of motion (ROM), the Mayo Elbow Performance Score (MEPS), and the severity of osteoarthritis were compared between the groups. RESULTS: Although preoperative elbow flexion and MEPS values were not significantly different between the groups, preoperative extension was significantly more restricted in group 2 than in group 1 (P = .0131). Group 2 tended to include more severe cases according to the Hastings-Rettig classification (P = .0693). ROM and MEPS values were improved in all cases. No significant differences in postoperative ROM or MEPS values were observed between the groups. There were no significant differences in the improvement in ROM or MEPS values between the 2 groups. CONCLUSIONS: The use of preoperative simulation and a color-coded bone model could help to achieve as good postoperative ROM and MEPS values for advanced elbow osteoarthritis as those for early and intermediate stages.

Degenerative changes in the elbow joint after radial head excision for fracture: quantitative 3-dimensional analysis of bone density, stress distribution, and bone morphology.

HYPOTHESIS AND BACKGROUND: Some investigators speculate that excision may lead to elbow arthritis and associated problems; however, evidence supporting this theory is limited. It is hypothesized that radial head excision causes bone density changes as a result of asymmetrical stress distributions, consequently leading to osteophyte formation. In this study, we sought to quantitatively compare the 3-dimensional (3D) bone density and stress distributions between operative and nonoperative elbows in patients who underwent radial head excision. Furthermore, we aimed to quantify the bone morphologic changes using 3D models in the same cohort. METHODS: After retrospective identification, this study enrolled 6 patients who had undergone radial head excision for radial head fractures. We created 3D bone models using computed tomography data obtained from the injured and uninjured elbows. Humerus and ulna models were divided into anatomic regions, and the bone density of each region was assessed and described by its percentage of high-density volume (%HDV). We also constructed finite element models and measured the stress values in each region. Furthermore, we compared the bone morphology by superimposing the operative elbow onto the mirror image of the nonoperative elbow. RESULTS: The mean interval from radial head excision to examination was 8.4 ± 3.3 years. The %HDV on the operative side was higher than that of the nonoperative side at the anterolateral trochlea (77.5% ± 6.5% vs. 64.6% ± 4.0%, P = .028) and posterolateral trochlea (70.7% ± 7.8% vs. 63.1% ± 3.8%, P = .034) regions of the distal humerus. Reciprocal changes were observed in the proximal ulna, as %HDV was higher in the lateral coronoid (52.6% ± 9.6% vs. 34.2% ± 6.6%, P = .007). The stress distributions paralleled the bone density measurements. The operative elbows demonstrated an enlarged capitellum and a widened and deepened trochlea with osteophyte formation compared with the nonoperative side. DISCUSSION AND CONCLUSION: In elbows treated with radial head excision, we identified asymmetrical bone density and stress alterations on the lateral side of the ulnohumeral joint and bone morphologic changes across the joint. These data support the theory that radial head excision contributes to ulnohumeral arthritis over the long term.

Bone resorption of the greater tuberosity after open reduction and internal fixation of complex proximal humeral fractures: fragment characteristics and intraoperative risk factors.

HYPOTHESIS AND BACKGROUND: In complex proximal humeral fractures, bone resorption of the greater tuberosity is sometimes observed after open reduction and internal fixation (ORIF). However, this has not been well characterized, and risk factors for resorption are not completely understood. We aimed (1) to identify the risk factors associated with bone resorption of the greater tuberosity and (2) to quantify the geometric and bone density characteristics associated with bone resorption using 3-dimensional computed tomography models in complex proximal humeral fractures treated with ORIF. METHODS: We identified a retrospective cohort of 136 patients who underwent ORIF of 3- or 4-part proximal humeral fractures; greater tuberosity resorption developed after ORIF in 30 of these patients. We collected demographic, fracture-related, and surgery-related characteristics and performed multivariable logistic regression analysis to identify factors independently associated with the development of greater tuberosity resorption. Furthermore, we identified 30 age- and sex-matched patients by use of propensity score matching to perform quantitative fragment-specific analysis using 3-dimensional computed tomography models. After the fragment of the greater tuberosity was identified, the number of fragments, the relative fragment volume to the humeral head, and the relative bone density to the coracoid process were calculated. Measurements were compared between matched case-control groups. RESULTS: We found that an unreduced greater tuberosity (odds ratio [OR], 10.9; P < .001), inadequate medial support at the calcar (OR, 15.0; P < .001), and the use of an intramedullary fibular strut (OR, 4.5; P = .018) were independently associated with a higher risk of bone resorption. Quantitative fragment-specific analysis showed that greater tuberosities with a larger number of fragments (5 ± 2 vs. 3 ± 2, P = .021), smaller fragments (9.9% ± 3.8% vs. 18.6% ± 4.7%, P < .001), and fragments with a lower bone density (66.4% ± 14.3% vs. 88.0% ± 18.4%, P = .001) had higher rates of resorption. DISCUSSION AND CONCLUSION: An unreduced greater tuberosity or inadequate medial support increases the risk of greater tuberosity resorption, as do a larger number of fracture fragments, smaller fragments, and lower bone density. Additionally, fibular strut grafting is an independent risk factor for tuberosity resorption. Further study is needed, but alternatives to strut grafting such as femoral head allograft may warrant serious consideration.

Parallel plate fixation for distal humeral fracture: Computer simulation to determine the appropriate screw insertion sequence.

BACKGROUND: Parallel plate fixation for distal humeral fractures provides good clinical outcomes. However, few studies have investigated the insertion sequence of the distal screws, although long screw insertion into the distal fragment is technically demanding. The purpose of this study was to investigate a correlation between the insertion sequence of the distal screws and the screw insertion difficulty. METHODS: Medial and lateral anatomical locking plates were closely fitted to the medial and lateral sides of the 10 intact humerus bone models on the computer. Most distal screws have 2 patterns: the screw was inserted from the lateral side first followed by insertion from the medial side (group 1) or from the medial side first followed by insertion from the lateral side (group 2). We calculated the target area wherein the second screw can be inserted. RESULTS: The length of the first most distal screw in group 2 was significantly longer than that in group 1 (58.4 vs. 49.8 mm, p < 0.05). The target areas in both groups were divided into the distal and proximal areas. The distal and proximal areas in group 1 were 91.6 and 61.6 mm2, respectively, and those in group 2 were 191.1 and 11.3 mm2, respectively. The distal area in group 2 was significantly greater than in the other areas (p < 0.05). CONCLUSIONS: In parallel plate fixation for distal humeral fracture, most distal screws could be more easily inserted from the medial side first followed by insertion from the lateral side than from the lateral side first followed by insertion from the medial side.

Comparison of tendon-bone healing between a newly developed ultrasound device and the conventional metallic drill in a rabbit MCL reconstruction model.

BACKGROUND: Ligament reconstructive surgeries demand tunnel creation using an over-drilling technique, though this technique has some problems such as metallic particle liberation or difficulties in tunnel creation other than circular cross-section. Recently, a new ultrasound (US) device for bone excavation to overcome these problems was developed. This study aimed to compare the tendon-bone healing in tunnels created using the new US device to that created using the conventional drill in a rabbit model. METHODS: A total of 72 rabbits underwent a reconstruction for the anterior half of the medial collateral ligament (MCL) using a half of the patellar tendon. For the femoral tunnel creation, a new US device was used in 36 rabbits (US group), while a conventional metallic drill was used for the remaining 36 rabbits (DR group). At 4, 8, and 12 weeks postoperatively, biomechanical (n = 10) and histological (n = 2) evaluations were performed. RESULTS: The ultimate failure load was almost equivalent between the US and DR groups at each period (US/DR; 4 weeks, 50.0 ± 12.8 N/43.4 ± 18.9 N, p = 0.62; 8 weeks, 78.6 ± 11.5 N/77.3 ± 29.9 N, p = 0.92; and 12 weeks: 98.9 ± 33.5 N/102.2 ± 38.3 N, p = 0.80). Pull-out failure from the femoral tunnel was only observed in two rabbits in the US group and one rabbit in the DR group at 4 weeks postoperatively. At 8 and 12 weeks, all specimens had a mid-substance tear. The collagen fiber continuity between tendon and bone occurred 8 weeks postoperatively in both groups and no histological difference was recognized throughout the evaluation period. CONCLUSIONS: The tunnels created using the new US device and the conventional drill had equivalent biomechanical and histological features in tendon-bone healing. The bone excavation technology by the new US device may be applicable in ligament reconstructive surgeries.

Quantitative Analysis for the Change in Lengths of the Radius and Ulna in Missed Bado Type I Monteggia Fracture.

BACKGROUND: In missed Monteggia fracture (MMF) cases, ulnar angulation and lengthening by osteotomy are required to reduce the dislocated radial head. This study aimed to clarify the abnormal discrepancy in length between the radius and ulna in MMF. We tested the hypothesis that the increase in the abnormal discrepancy in length between the radius and ulna relates with the duration of radial head dislocation. METHODS: In total, 24 patients with MMF were studied and classified into 2 groups, according to the duration of radial head dislocation, including the early group (n=9, within 3 y) and the long-standing group (n=15, older than 3 y). The lengths of the radius (Lr) and ulna (Lu) were measured. The difference in length between the ulna and radius (DL=Lu-Lr) was calculated on both the affected (DLaff) and normal (DLnor) sides. DLnor-DLaff, which represented an abnormal discrepancy in both bones, was analyzed for correlation with the duration of radial head dislocation and the age at initial injury. RESULTS: The affected and normal sides had no differences in the Lr of both the groups and in the Lu of the early group. However, in the long-standing group, Lu was significantly smaller in the affected side than in the normal side (P=0.001). In the long-standing group, DLaff was significantly smaller, owing to decreased length of the ulna, than DLnor (P=0.003). The DLnor-DLaff was positively correlated with the duration of radial head dislocation and was negatively correlated with the age at injury. CONCLUSIONS: In chronic MMF cases, the length of the ulna was shorter in the affected side than in the normal side. Therefore, ulnar lengthening is necessary to resolve this abnormal discrepancy and reduce the radial head. Because excessive ulnar lengthening has risks of postoperative complications, one of the surgical options is gradual ulnar lengthening or shortening osteotomy of the radius. LEVEL OF EVIDENCE: Level III-Prognosis study.

Intra-articular corrective osteotomy for intra-articular malunion of distal radius fracture using three-dimensional surgical computer simulation and patient-matched instrument.

BACKGROUND: Corrective osteotomy of malunited intra-articular distal radius fracture is challenging. In this study, we investigated the results in patients with malunited intra-articular distal radius fracture who underwent intra-articular corrective osteotomy through an extra-articular approach using three-dimensional (3-D) computer simulation and a patient-matched instrument (PMI). METHODS: We retrospectively studied five consecutive patients with symptomatic malunited intra-articular distal radius fracture who underwent corrective osteotomy using a PMI. The maximal step-off on computed tomography and the deformity angle on plain radiographs were evaluated. The clinical examination parameters included range of motion (ROM), grip strength, pain according to visual analog scale (VAS), and Patient-Rated Wrist Evaluation (PRWE) score. RESULTS: The maximal step-off was significantly reduced from 4.9 ± 1.8 to 1.0 ± 0.2 mm (p = 0.008). The absolute differences between the affected side and the normal contralateral side in radial inclination were significantly reduced from 5.4° ± 3.4°-1.2° ± 1.1° (p = 0.043). These differences were not significantly reduced postoperatively in the volar tilt and ulnar variance. VAS was significantly reduced from 4.1 ± 1.6 to 0.9 ± 0.7 cm (p = 0.006). The PRWE score significantly improved from 41.6 ± 22.0 to 15.7 ± 19.5 (p = 0.043). Grip strength was significantly increased from 54.0% ± 14.8%-85.8% ± 18.8% (p = 0.003). The preoperative and postoperative total arc of the wrist and forearm ROM were not significantly different. CONCLUSIONS: Intra-articular corrective osteotomy using PMI could be one of the reliable treatment options for intra-articular malunion. PMI has exceptionally high precision performance, and it is also anticipated to yield superior surgical results.

The morphologic change of the elbow with flexion contracture in upper obstetric brachial plexus palsy.

BACKGROUND: Contracture of the elbow after obstetric brachial plexus palsy (OBPP) is well known; however, details of the 3-dimensional (3D) morphologic changes in the elbow joint in OBPP have not been clarified. This study aimed to clarify the 3D morphologic changes in the elbow joint by focusing on the distal humerus with flexion contracture in upper OBPP. We tested the hypothesis that the shape of the distal humerus with flexion contracture in upper OBPP is hypoplastic in the trochlea, capitellum, and olecranon fossa. METHODS: We retrospectively studied 20 patients with elbow flexion contracture and residual OBPP. The approximate radius of the distal humerus, the shortest distance between the olecranon and coronoid fossa, and the size of the olecranon fossa were measured and compared between the affected and normal sides using 3D bone models to assess the distal humerus morphology. RESULTS: The average radius of the distal humerus was smaller on the affected side than on the normal side. Furthermore, the average distance between the olecranon and coronoid fossa was greater and the average size of the olecranon fossa was smaller on the affected side than on the normal side. The size of the distal humerus was significantly smaller and the olecranon fossa was significantly shallower on the affected side. CONCLUSIONS: Consistent with our original hypothesis, the distal humerus with flexion contracture in upper OBPP was hypoplastic. The shallow olecranon fossa might prevent full extension of the elbow even though soft tissue contracture release is performed. We recommend evaluation of the morphology of the olecranon fossa to determine the treatment plan for elbow flexion contracture with OBPP.

Validation of the registration accuracy of navigation-assisted arthroscopic débridement for elbow osteoarthritis.

BACKGROUND: The identification and precise removal of bony impingement lesions during arthroscopic débridement arthroplasty for elbow osteoarthritis is technically difficult. Surgical navigation systems, combined with preoperative 3-dimensional (3D) assessment of bony impingements, can provide real-time tracking of the surgical instruments and impingement lesions. This study aims to determine the registration accuracy of the navigation system for the humerus and ulna during elbow arthroscopy. METHODS: We tested the registration procedure using resin bone models of 3 actual patients with elbow osteoarthritis. We digitized bone surface points using navigation pointers under arthroscopy. We initially performed paired-point registration, digitizing 6 preset anatomical landmarks, and then refined the initial alignment with surface matching registration, digitizing 30 points. The registration accuracy for each trial was evaluated as the mean target registration error in each reference marker. Three observers repeated the registration procedure 5 times each with the 3 specimens (total, 45 trials). The median of the registration accuracy was evaluated in total (45 trials) as the accuracy of the registration procedure. The differences in the registration accuracy among the 3 observers (median of 15 trials) were also examined. RESULTS: The total registration accuracies were 0.96 mm for the humerus and 0.85 mm for the ulna. No significant differences were found in the registration accuracy for the humerus and ulna among the 3 observers. CONCLUSIONS: This arthroscopic-assisted registration procedure is sufficiently feasible and accurate for application of the navigation system to arthroscopic débridement arthroplasty in clinical settings.

Rotational and Varus Instability in Chronic Lateral Ankle Instability: In Vivo 3D Biomechanical Analysis.

We retrospectively evaluated the altered biomechanics of the talus in 15 adult patients (7 males, 8 females) with chronic lateral ankle instability when the ankle joint moved actively from full dorsiflexion to full plantarflexion under a non-weight bearing condition. CT images were taken for the unstable ankle and the contralateral normal (control) ankle. Three-dimensional surface models of both ankle joints were reconstructed from the CT data, and we used a computer simulation program to compare both ankle motions of inversion/eversion in the coronal plane, plantarflexion/dorsiflexion in the sagittal plane, and internal rotation/external rotation in the axial plane. This evaluation method provides in vivo, dynamic, and 3D results of ankle motion. In the ankles with chronic lateral instability and the controls, the average talar rotational movement of inversion (+)/eversion (-) was 19.0° and 15.5° and the internal rotation (+)/external rotation (-) was 30.4° and 20.7°, respectively. Paired t-tests revealed significant differences in the amount of inversion (+)/eversion (-) (p=0.012) and internal rotation (+)/external rotation (-) (p<0.001) between unstable and normal ankle joints. The difference of mean rotational movement in internal rotation (9.7°) was greater than that of inversion (3.5°). Rotational instability should be considered when evaluating chronic lateral ankle instability.

Rotational Corrective Osteotomy for Malunited Distal Diaphyseal Radius Fractures in Children and Adolescents.

PURPOSE: To report our method of computer-planned rotational corrective osteotomy for malunited distal diaphyseal radius fractures in children and adolescents using a custom jig and to review the results of 4 cases. METHODS: Four patients (mean age, 13 years; range, 11-16 years) underwent computer-planned rotational corrective osteotomy for malunited distal diaphyseal radius fracture using a custom jig. We retrospectively evaluated their radiographic and clinical data. RESULTS: In patients who had marked restriction of forearm supination before osteotomy, the mean arc of forearm supination improved from 5° before surgery to 79° after surgery. Angular deformity on x-ray, range of forearm rotation, and grip strength all improved after surgery. Mild and moderate pain reported by 1 and 2 patients, respectively, was resolved after surgery. CONCLUSIONS: Computer-planned rotational corrective osteotomy for malunited distal diaphyseal radius fracture in children and adolescents using a custom jig is a strategy that facilitates the surgical procedure by accurately correcting both rotational and angular deformities on 1 plane in a single procedure. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

In Vivo 3-Dimensional Kinematics of Thumb Carpometacarpal Joint During Thumb Opposition.

PURPOSE: This study primarily aimed to demonstrate the screw-home rotation of the thumb carpometacarpal (CMC) joint and the function of surrounding ligaments during thumb oppositional motion. METHODS: A 3-dimensional kinematic analysis of the thumb CMC joint was conducted using data derived from computed tomography of 9 healthy volunteers. Scans were obtained in the neutral forearm and wrist position and the thumb in maximum radial abduction, maximum palmar abduction, and maximum opposition. The movements of the first metacarpal and the palmar and dorsal bases on the trapezium during thumb oppositional motion from radial abduction through palmar abduction were quantified using a coordinate system originating on the trapezium. In addition to the kinematic analyses, the length of virtual ligaments, including the anterior oblique, ulnar collateral, dorsal radial, dorsal central (DCL), and posterior oblique ligament (POL), were calculated at each thumb position. RESULTS: From radial abduction to opposition of the thumb through palmar abduction, the first metacarpal was abducted, internally rotated, and flexed on the trapezium. The palmar base of the first metacarpal moved in the palmar-ulnar direction, and the dorsal base moved in the palmar-distal direction along the concave surface of the trapezium. Although the DCL and POL lengthened, the lengths of other ligaments did not change significantly. CONCLUSIONS: During thumb oppositional motion, internal rotation of the first metacarpal occurred, with the palmar base rotating primarily with respect to the dorsal base. The DCL and POL may be strained in thumb functional positions. CLINICAL RELEVANCE: Kinematic variables indicated a screw-home rotation of the thumb CMC joint and the contribution of the dorsal ligaments to the stability of the rotation on the pivot point.

Corrective osteotomy for hyperextended elbow with limited flexion due to supracondylar fracture malunion.

BACKGROUND: Extension deformity of the distal humerus after a malunited supracondylar fracture can restrict elbow flexion. Here we report a computer-assisted operative procedure and review the results of clinical cases in which corrective surgery was performed. METHODS: The medical records of the patients who underwent corrective osteotomy for hyperextended elbow malunion of the distal humerus with limited elbow flexion (flexion angle ≤100°) were reviewed retrospectively. Osteotomy was performed using patient-specific instruments designed based on preoperative 3-dimensional computer simulation. RESULTS: Three patients, a 55-year-old woman and two 12-year-old boys, met the inclusion criteria. The angles of hyperextension of the affected distal humerus were 29°, 29°, and 25°, respectively. The range of flexion/extension of the elbow motion in the first patient improved from 95°/25° preoperatively to 140°/-10° postoperatively, in the second patient from 100°/20° to 145°/5°, and in the third patient from 80°/25° to 140°/10°. Bone union was achieved in all patients. There were no major complications. The corrective operations not only improved elbow flexion but also increased the total range of motion in the elbow by rebuilding the anterior curve of the distal humerus. CONCLUSIONS: Correction of the extension deformity of the distal humerus after a malunited supracondylar fracture is a reasonable option for patients older than 10 years with restricted elbow flexion. Preoperative computer simulation and the use of patient-specific instruments can be a useful alternative that enables accurate deformity correction and improves the total range of motion.

Three-dimensional scapular dyskinesis in hook-plated acromioclavicular dislocation including hook motion.

BACKGROUND: The purpose of this study is to analyze the 3-dimensional scapular dyskinesis and the kinematics of a hook plate relative to the acromion after hook-plated acromioclavicular dislocation in vivo. Reported complications of acromioclavicular reduction using a hook plate include subacromial erosion and impingement. However, there are few reports of the 3-dimensional kinematics of the hook and scapula after the aforementioned surgical procedure. METHODS: We studied 15 cases of acromioclavicular dislocation treated with a hook plate and 15 contralateral normal shoulders using computed tomography in the neutral and full forward flexion positions. Three-dimensional motion of the scapula relative to the thorax during arm elevation was analyzed using a computer simulation program. We also measured the distance from the tip of the hook plate to the greater tuberosity, as well as the angular motion of the plate tip in the subacromial space. RESULTS: Decreased posterior tilting (22° ± 10° vs 31° ± 8°) in the sagittal plane and increased external rotation (19° ± 9° vs 7° ± 5°) in the axial plane were evident in the affected shoulders. The mean values of translation of the hook plate and angular motion against the acromion were 4.0 ± 1.6 mm and 15° ± 8°, respectively. The minimum value of the distance from the hook plate to the humeral head tuberosity was 6.9 mm during arm elevation. CONCLUSIONS: Acromioclavicular reduction using a hook plate may cause scapular dyskinesis. Translational and angular motion of the hook plate against the acromion could lead to subacromial erosion. However, the hook does not seem to impinge directly on the humeral head.