Avoiding the posterior interosseous nerve during 2-incision distal biceps tendon repair: an anatomic study.

BACKGROUND: The posterior interosseous nerve (PIN) is the most commonly injured motor nerve during distal biceps tendon repair resulting in severe functional deficits. Anatomic studies of distal biceps tendon repairs have evaluated the proximity of the PIN to the anterior radial shaft in supination, but limited studies have evaluated the location of the PIN in relation to the radial tuberosity (RT), and none have examined its relation to the subcutaneous border of the ulna (SBU) with varying forearm rotation. This study evaluates the location of the PIN in relation to the RT and SBU to help guide surgeons in safe placement of the dorsal incision and the safest zones of dissection. METHODS: The PIN was dissected from arcade of Frohse to 2 cm distal to the RT in 18 cadaver specimens. Four lines were drawn perpendicular to the radial shaft at the proximal, middle, and distal aspect of and 1 cm distal to the RT in the lateral view. Measurements were recorded with a digital caliper along these lines to quantify the distance between the SBU and RT to the PIN with the forearm in neutral, supination, and pronation with the elbow at 90° flexion. Measurements were also made along the length of the radius at the volar, middle, and dorsal surfaces at the distal aspect of the RT to assess its proximity to the PIN. RESULTS: Mean distances to the PIN were greater in pronation than supination and neutral. The PIN crossed the volar surface of the distal aspect of the RT -6.9 ± 4.3 mm (-13, -3.0) in supination, -0.4 ± 5.8 mm (-9.9, 2.5) in neutral, and 8.5 ± 9.9 mm (-2.7, 13) in pronation. One centimeter distal to the RT, mean distance to the PIN was 0.54 ± 4.3 mm (-4.5, 8.8) in supination, 8.5 ± 3.1 mm (3.2, 14) in neutral, and 10 ± 2.7 mm (4.9, 16) in pronation. In pronation, mean distances from the SBU to the PIN at points A, B, C, and D were 41.3 ± 4.2, 38.1 ± 4.4, 34.9 ± 4.2, and 30.8 ± 3.9 mm, respectively. CONCLUSION: PIN location is quite variable, and to avoid iatrogenic injury during 2-incision distal biceps tendon repair, we recommend placement of the dorsal incision no more than 25 mm anterior to the SBU and carrying out deep dissection proximally first to identify the RT before continuing the dissection distally to expose the tendon footprint. The PIN was at risk of injury along the volar surface at the distal aspect of the RT in 50% with neutral rotation and 17% with full pronation.

Preoperative radius head dislocation affects forearm rotation after mobilization of congenital radioulnar synostosis.

BACKGROUND: The present study was carried out to answer three questions: 1) How much forearm rotation can be expected after mobilization of congenital radioulnar synostosis (CRUS)? 2) Does preoperative radius head dislocation affect forearm rotation after mobilization? 3) What factors other than radius head dislocation affect postoperative forearm rotation? METHODS: We performed mobilization of CRUS with a free vascularized fascio-fat graft and a radius osteotomy (Kanaya's procedure) on 26 forearms of 25 patients. The age at the surgery ranged from 5.3 to 13.4 years. The follow-up duration ranged 24-111 months. We classified CRUS into 3 groups according to the dislocation of the radius head: posterior dislocation (N = 13), anterior dislocation (N = 9) and no dislocation (N = 4). Since major complaints of patients and parents were poor forearm rotation and lack of supination, they were evaluated separately. RESULTS: Mean preoperative forearm ankylosis angle was 34.8° (range; neutral to 90° pronation). Preoperative pronation ankylosis angle was higher in the posterior dislocation group (mean 55.3°) than the anterior dislocation (mean 11.6°) and no dislocation groups (mean 5.0°). There was no re-ankylosis after mobilization and the mean postoperative active range of motion (ROM) was 86.5°. The mean active ROM was 75.7° in the posterior dislocation group, 96.1° in anterior dislocation group and 100.0° in no dislocation group. The mean active supination was 6.9, 33.9 and 47.5° respectively. The posterior dislocation group showed less ROM and less supination than other groups. Preoperative pronation ankylosis angle showed negative correlation with postoperative ROM (ρ = - 0.59) and postoperative supination (ρ = - 0.73). CONCLUSION: The mean postoperative active ROM of this mobilization was 86.5°. Posterior dislocation group showed higher pronation ankylosis angle preoperatively, and less postoperative ROM and less supination than anterior and no dislocation groups. Preoperative pronation ankylosis angle showed negative correlation with postoperative ROM and supination.

Influence of forearm rotation on the kinetic stabilizing efficiency of the muscles that control the scapholunate joint. Clinical application in proprioceptive and neuromuscular rehabilitation programs.

BACKGROUND: This study focuses on the relationship between forearm muscles, carpal ligaments, and their impact on scapholunate joint stability across varying forearm rotations. This is crucial for optimizing pre and postoperative rehabilitation strategies for scapholunate joint dysfunction. PURPOSE: Our study aims to understand the kinetic influence of forearm muscles on scapholunate joint instability. We emphasize the significance of forearm rotation to enhance treatment efficacy. STUDY DESIGN: We conducted an experimental study to understand how forearm muscles contribute to the stability of the scapholunate joint during different degrees of forearm rotation and we focused on the joint effect of muscle groups rather than individual muscles for treatment protocols. RESULTS: Our findings shed light on the conservative treatment of dynamic scapholunate instability and the postoperative rehabilitation of scapholunate ligament repair. We found that the effect of forearm muscles significantly contributes to preserve stability in the scapholunate joint across various forearm rotational positions. These insights have practical implications for hand therapists, offering innovative strategies to enhance clinical practice. CONCLUSIONS: This research underscores the importance of considering forearm rotation when developing rehabilitation protocols for scapholunate joint instability and provides a valuable perspective in line with current rehabilitation principles.

Length Changes in the Interosseous Membrane During Forearm Rotation: A 3-Dimensional Study In Vivo.

PURPOSE: The length change of the interosseous membrane (IOM) during forearm rotation has not been fully studied. To explore the meaning of length change in the distal oblique band (DOB), the distal accessory band (DAB), and the proximal, middle, and distal parts of the central band (CBP, CBM, and CBD, respectively), we investigated the length change in these ligaments at maximum pronation, 45° of pronation, neutral position, 45° of supination, and maximum supination in vivo. METHODS: The images of the right forearms from 6 healthy volunteers were obtained by computed tomography scanning at the 5 above-mentioned rotation positions. We created 3-dimensional models of the radius and ulna, DOB, DAB, and central band based on the points of origin and insertion. Finally, the length of each ligament was estimated from the points of insertions and origins registered on the 3-dimensional models. RESULTS: The DAB and CBD lengths increased significantly from maximum pronation to 45° of pronation. The DOB length increased significantly from 45° of pronation to neutral position and decreased significantly from 45° of supination to maximum supination. The DAB and CBM lengths increased significantly from neutral position to 45° of supination. The DAB length decreased significantly from 45° of supination to maximum supination. For the CBP, no difference in length was observed during forearm rotation. CONCLUSIONS: The DOB becomes taut at neutral position, and the central band, especially the CBP, is nearly isometric. The findings indicate that the DOB may provide the primary stabilization of the distal radioulnar joint and that the central band is the key stabilizer during forearm rotation. CLINICAL RELEVANCE: Surgeons may pay attention to the DOB when a patient incurs a distal radioulnar joint injury, and the CBP may be the optimal location for IOM reconstruction.

Reliability of the Dorsal Tangential View in Assessment of Distal Radioulnar Joint Reduction in the Neutral, Pronated, and Supinated Positions in a Cadaver Model.

PURPOSE: Intraoperative assessment of distal radioulnar joint (DRUJ) alignment is often based on lateral radiographs whose interpretation is dependent upon positioning the forearm in neutral rotation. The dorsal tangential view (DTV) is a near-axial view of the dorsal wrist used in assessing dorsal screw penetration during radius fixation. The purpose of this study was to determine whether the DTV can also reliably assess DRUJ alignment in multiple forearm positions. METHODS: Four transhumeral cadaveric specimens were used to simulate an unstable DRUJ. The stabilizing soft tissue structures of the DRUJ were sectioned. Fluoroscopic DTV images were obtained with the DRUJ of each specimen held in 5 positions: dorsally dislocated, dorsally subluxated, reduced, volarly subluxated, and volarly dislocated. In each position, images were taken with the forearm in neutral rotation, full pronation, and full supination. Three observers independently assessed DRUJ position on DTV images. Intra- and interobserver reliability were assessed in each forearm position. RESULTS: Observers correctly identified DRUJ position as reduced, volarly malreduced, or dorsally malreduced on 94% of the DTV images (97%, 95%, and 92% in the neutral, supinated, and pronated forearm positions, respectively). Weighted kappa values for intraobserver reliability were 0.965, 0.964, and 0.965 for the 3 observers. The mean kappas for intraobserver reliability were 1.000, 0.967, and 0.930 with the forearm in neutral, supinated, and pronated positions, respectively. Weighted kappa values for interobserver reliability between paired observers were 0.948, 0.912, and 0.929. The mean kappa for interobserver reliability was 0.926, 0.931, and 0.930 for the forearm in neutral, supinated, and pronated positions, respectively. CONCLUSIONS: The DTV reliably demonstrated the position of the DRUJ independent of forearm rotation in a cadaveric model. CLINICAL RELEVANCE: Surgeons may consider the DTV as another tool for fluoroscopic verification of the DRUJ reduction in the operating room or clinic.

A new pathologic classification for elbow stiffness based on our experience in 216 patients.

BACKGROUND: Elbow stiffness commonly causes functional impairment and upper-limb disability. This study aimed to develop a new pathologic classification to further understand and standardize elbow arthrolysis from a new perspective, as well as to determine clinical outcomes. METHODS: Extension-flexion dysfunction was classified into 4 types: EFI, tethers alone; EFII, tethers with blocks; EFIII, articular malformation; and EFIV, bony ankylosis. Forearm rotation dysfunction was classified into 3 types: FRI, contracture alone; FRII, radial head malunion or nonunion; and FRIII, proximal radioulnar bony ankylosis. A total of 216 patients with elbow stiffness were prospectively included and categorized preoperatively. All surgical procedures were performed by the same chief surgeon; different types underwent specific procedures. Patient data, elbow motion, and functional scores were analyzed. RESULTS: Mean range of motion (ROM) increased from 40° preoperatively to 118° at final follow-up; 88% of patients regained ROM of 100° or greater. The forearm rotation arc (FRA) with forearm rotation dysfunction increased from a preoperative mean of 76° to 128°; 82% of patients regained an FRA of 100° or greater. The mean Mayo Elbow Performance Index (MEPI) increased from 63 to 91 points; the proportion of patients with good or excellent results was 95%. EFI patients had the best ROM (129°) and MEPI (93 points) and EFIV patients achieved the most-changed ROM (116°), whereas EFIII patients had the worst ROM (104°) and MEPI (84 points) and the least-changed ROM (64°). The FRA was best in FRI patients (142°), followed by FRII patients (118°), and worst in FRIII patients (82°); in contrast, the changed FRA was greatest in FRIII patients (82°), followed by FRII patients (64°), and least in FRI patients (37°). CONCLUSION: This study suggests that the proposed pathologic classification provides a new perspective on the understanding and standardization of elbow arthrolysis, providing satisfactory clinical outcomes.

Loss of pronation-supination in patients with heterotopic ossification around the elbow.

BACKGROUND: Heterotopic ossification (HO) is a well-recognized cause of limited flexion-extension, but it can also limit pronation-supination. There is a paucity of literature concerning restriction of pronation-supination due to HO. METHODS: We conducted a retrospective review of patients who had undergone elbow surgery for HO removal between January 1, 2003, and September 27, 2013. Computed tomography scans were reviewed to determine the presence of HO restricting forearm rotation and were rated independently by 4 observers. Each elbow was given 1 of 4 scores according to the likelihood that HO was restricting forearm rotation. Agreement was achieved when 3 or 4 observers thought that HO definitely or probably caused a loss of pronation-supination. RESULTS: Of 132 post-traumatic patients undergoing HO excision for restricted elbow motion, 61 (46%) also lacked a functional arc of pronation and supination (50° and 50°, respectively). Of these 61 patients, 32 (53%) were considered to have lost forearm rotation because of HO. The remaining 29 patients (47%) were thought to have restricted forearm rotation for reasons unrelated to HO. DISCUSSION: In this study, loss of pronation-supination affected almost half of the patients (61 of 132 [46%]) undergoing HO excision around the elbow. Of these 61 patients, 32 (52%) had HO extending into the proximal forearm and affecting rotation. From our data, one can expect that about one-quarter (24% of patients in this study, or 32 of 132) with post-traumatic HO of the elbow will have a significant functional loss of pronation-supination due to HO extending into the forearm.

Axial load transmission through the elbow during forearm rotation.

BACKGROUND: Forearm rotation is closely associated with the axiorotational force transmission through the elbow joint. A technique has been developed to study the transmission of force across the radiocapitellar and ulnotrochlear joints during forearm rotation. METHODS: Ten human cadaveric upper limbs were prepared on a custom-designed apparatus that permits the application of extrinsic axial loads across an intact cadaveric elbow joint. A force-sensitive transducer was inserted into the elbow joint of each cadaver. A 160 N axial force was applied to the specimen during cyclic forearm rotation while the force, contact pressure, and contact area through the elbow joint were measured. RESULTS: The mean force across the radiocapitellar joint showed no significant difference between pronation and supination (P = .3547). The radiocapitellar joint showed significantly higher contact area (P = .0001) and lower contact pressure (P = .0001) in pronation than in supination. The mean values for contact pressure, area, and force across the ulnotrochlear joint were not significantly different between supination and pronation. CONCLUSION: The contact pressure and contact area of the radiocapitellar joint in the cadaveric model changed according to forearm rotation while the force remained constant. The mean contact pressure of the radiocapitellar joint in pronation was significantly lower than that in supination because the force across it did not change significantly and its contact area decreased significantly. These findings may suggest that the pronated elbow can play an important role in protecting the radiocapitellar joint in high-impact activities like delivering punch in martial arts or falling on an outstretched arm.

Open arthrolysis for elbow stiffness increases carrying angle but has no impact on functional recovery.

BACKGROUND: With the exception of normal anatomic changes in the medial collateral ligament and radial head, other factors related to carrying angle changes have not been systematically studied. We reviewed patients who underwent open arthrolysis of the elbow, and evaluated if open arthrolysis could change carrying angle. We then identified factors associated with carrying angle changes. METHODS: Fifty patients with a minimum of 24 months of follow-up after open arthrolysis were evaluated retrospectively. Preoperative and postoperative carrying angles were compared. RESULTS: The carrying angles of 36 elbows in 36 patients were unchanged after surgery (Group A), while the carrying angles of 14 elbows in 14 patients increased postoperatively (Group B). In Group A, mean postoperative extension and flexion were 7° (range 0-24°) and 125° (range 10-135°) respectively, while mean postoperative pronation and supination were 60° (range 50-80°) and 65° (range 30-85°), respectively. In Group B, mean postoperative extension and flexion were 25° (range 0-40°) and 128° (range 60-138°), while mean postoperative pronation and supination were 65° (range 45-85°) and 60° (range 45-75°), respectively. No significant difference in range of motion and Mayo Elbow Performance Score was observed between the two groups. CONCLUSIONS: During open arthrolysis, humeral trochlea debridement and techniques for improving forearm rotation could increase carrying angle. However, this had no impact on elbow functional recovery.

In vivo three-dimensional elbow biomechanics during forearm rotation.

BACKGROUND: It is unclear how elbow kinematics changes during forearm rotation. This study investigated in vivo 3-dimensional elbow kinematics during forearm rotation. METHODS: We studied 12 normal elbows using in vivo 3-dimensional computed tomography data in maximum forearm supination, neutral, and maximum pronation with the elbows in extension. We measured the motion of the radius and ulna relative to the humerus using a markerless bone registration technique and the contact area of the radiocapitellar joint, proximal radioulnar joint, and ulnohumeral joint using a proximity mapping method. RESULTS: When the forearm rotated from the supinated position to the pronated position, the radius showed significant varus rotation, internal rotation, and extension relative to the humerus. The center of the radial head significantly translated anteriorly, proximally, and laterally. The ulna significantly rotated in valgus, and the deepest point on the sagittal ridge of the trochlear notch translated medially with forearm pronation. The contact area of the radiocapitellar joint was largest in pronation. The contact area of the proximal radioulnar joint was largest in supination. The contact area of the ulnohumeral joint showed no significant change during forearm rotation. CONCLUSIONS: In pronation, because of the proximal migration of the radial head, the radiocapitellar joint was most congruent compared with other positions. The proximal radioulnar joint was most congruent in supination. The ulnohumeral joint congruency was not affected by forearm rotation. This study provides useful information for understanding 3-dimensional elbow motion and joint osseous stability related to forearm rotation.

The inter-rater reliability of the modified finger goniometer for measuring forearm rotation.

STUDY DESIGN: Prospective cohort study. PURPOSE OF THE STUDY: To compare the inter-rater reliability of using a modified finger goniometer (MFG) for the measurement of isolated forearm rotation for patients with distal radius fractures to the currently accepted technique for isolated forearm measurement. INTRODUCTION: The currently accepted method of forearm measurement requires the assessor to visually estimate vertical for the stationary arm and placement of the moveable arm while placing a straight edge along a curved surface. Inter-rater reliability may be limited as assessors may estimate the placement of the goniometer arms differently depending on their experience, posture, and even their positioning relative to the patient. Rather than continue to place a straight edge on a round surface, we evaluate a new technique using an MFG for measuring isolated forearm rotation. METHODS: Patients with clinically healed distal radius fractures were enrolled in the study. Measurement of active forearm pronation and supination was recorded using 2 separate measurement techniques. These measurements were taken by 2 separate hand therapists with more than 10 years of clinical experience in a tertiary care setting at the beginning and end of hand therapy sessions for 3 consecutive weekly visits. Intraclass correlation coefficients (ICCs), standard error of measurement, and minimal detectable change were calculated for each technique. RESULTS: The point estimates for the MFG method demonstrated a slightly higher ICC than the standard method for pronation (0.86 vs 0.82). For supination, both measurement techniques displayed equally high pooled ICCs (0.95). The standard error of measurements for the MFG were 2.1 for pronation and 1.2 for supination compared with 2.9 (pronation) and 1.2 (supination) for the standard technique. These translate into 90% minimal detectable changes of 5° and 3° for the MFG pronation/supination compared with 7° (pronation) and 3° (supination) for the standard technique, respectively. DISCUSSION: Although the point estimates for the ICCs of the MFG method are equal or higher than the standard method, the confidence intervals for the ICCs overlap, indicating that the MFG is at least equivalent to the standard method in terms of inter-rater reliability. LEVEL OF EVIDENCE: 2b.

How does wrist position affect the length of the distal radioulnar ligament: a three-dimensional image study in vivo?

PURPOSE: This study was designed to investigate the length changes of the distal radioulnar ligament at different wrist positions and to determine the effect of hyperextension on the distal radioulnar ligament and to find out the most vulnerable position where the distal radioulnar ligament rupture and foveal avulsion. METHODS: We obtained computed tomography scans of the wrists for 12 volunteers including two groups: hyperextension group and hyperextension with maximal rotation group. The images were reconstructed to the three-dimensional bone structures with customized software. The four portions of the distal radioulnar ligament were measured and analyzed statistically. RESULTS: No significant differences were noted in the lengths of the each portion of the distal radioulnar ligament among neutral position, wrist hyperextension, and hyper-radial extension. From neutral position to hyperextension with maximal pronation, the lengths of the palmar superficial radioulnar ligament (psRU) and dorsal deep radioulnar ligament (ddRU) decreased significantly, whereas the dorsal superficial radioulnar ligaments (dsRU) and palmar deep radioulnar ligament (pdRU) increased significantly. From neutral position to hyperextension with maximal supination, the lengths of the pdRU and dsRU ligaments decreased significantly, and the lengths of psRU and ddRU ligaments changed little. CONCLUSIONS: The factor of hyperextension has little effect on the length of the distal radioulnar ligament and the distal radioulnar ligament may be under great tension at the position of hyperextension with maximal pronation. These findings can provide more information to understand the pathomechanics of the triangular fibrocartilage complex injury caused by a fall on the outstretched hand and can provide information relevant to the distal radioulnar ligament restoration.

Squared ligament of the elbow: anatomy and contribution to forearm stability.

OBJECTIVE: The present study describes the macroscopic and microscopic features of the squared ligament of the elbow (SLE). In addition, the SLE biomechanical behavior and contribution to the forearm stability were also examined. MATERIALS AND METHODS: Ten forearms from freshly frozen cadavers were used for this work. Each forearm was mounted in an experimental frame for quantification of longitudinal and transverse stability. Macroscopic features and biomechanical behavior were analyzed on dynamic videos obtained during forearm rotation. Then, the SLE was harvested from the 10 forearms for microscopic analysis on histological slices stained with hematoxylin-eosin-saffron. RESULTS: Two main SLE configurations were identified. One in which the SLE had three distinct bundles (anterior, middle, posterior) and another in which it was homogeneous. The anterior part of the SLE had a mean length of 11.2 mm (±2.4 mm) and a mean width of 1.2 mm (±0.2 mm) while the posterior part had a mean length of 9.9 mm (±2.2 mm) and a mean width of 1 mm (±0.2 mm). Microscopic examination showed that the SLE is composed of a thin layer of arranged collagen fibers. During forearm rotation, the SLE progressively tightens upon pronation and supination by wrapping around the radial neck. Tightening of the SLE during forearm rotation provides transverse and longitudinal stability to the forearm, mainly in maximal pronation and supination. CONCLUSION: The SLE is a true ligament and provides forearm stability when it is stretched in pronation and supination.

Proconsul heseloni distal radial and ulnar epiphyses from the Kaswanga Primate Site, Rusinga Island, Kenya.

Only two distal epiphyses of a radius and ulna are consensually attributed to the holotype skeleton of Proconsul heseloni, KNM-RU 2036. Here, we describe seven adult and immature distal antebrachial (radial and ulnar) epiphyses from two other individuals of P. heseloni from the Lower Miocene deposits of the Kaswanga Primate Site (KPS), Rusinga Island, Kenya. Because KNM-RU 2036 and KNM-KPS individuals III and VIII are conspecific and penecontemporaneous, their comparison provides the opportunity i) to characterize, for the first time, the morphological variation of the distal radioulnar joint in a Miocene ape, P. heseloni, and ii) to investigate the functional and evolutionary implications. Our results show that the distal antebrachial epiphyses of KNM-KPS III and VIII correspond to stages of bone maturation that are more advanced than those of KNM-RU 2036 (larger articulations and sharper articular borders and ligament attachments that are more developed). Accordingly, functional interpretations based solely on the skeleton of KNM-RU 2036 have involved an underestimation of the forearm rotation abilities of P. heseloni. In particular, the KPS fossils do not exhibit the primitive morphology of distal radioulnar syndesmosis, as those of KNM-RU 2036 and most nonhominoid primates, but rather the morphology of an incipient diarthrosis (as in extant lorisines and hominoids). The distal radioulnar diarthrosis permits more mobility and maintenance of the wrist during repeated and slow rotation of the forearms, which facilitates any form of quadrupedal locomotion on discontinuous and variably oriented supports. By providing the oldest evidence of a distal radioulnar joint in an early Miocene hominoid, the main conclusions of this study are consistent with the role of cautious climbing as a prerequisite step for the emergence of positional adaptations in apes.

Identification of overlengthening after replacement of the radial head with a bipolar prosthesis.

INTRODUCTION: Overlengthening of the radial column leads to insufficient functionality and increased capitellar wear. Methods to detect or prevent overlengthening have been described for monopolar prostheses. The aim of this study was to evaluate whether one such method described by Athwal et al. is also applicable for a bipolar prosthesis. MATERIALS AND METHODS: The radial heads of six fresh frozen upper extremities were resected. A bipolar radial head prosthesis was implanted in each, and the effects of sequential overlengthening on the alignment of the radiocapitellar and ulnohumeral joint line were recorded by fluoroscopic images. Digital image analysis and estimation of overlengthening followed according to the method described by Athwal et al. RESULTS: Statistical analysis of the estimated and actual differences between the native state and bipolar replacement of the radial head with stepwise overlengthening of 1.5, 3, 4.5, and 6 mm showed a specificity of 86 % but consistently underestimated the amount of overlengthening with a sensitivity of only 61 %. DISCUSSION: The method described by Athwal et al. for the identification of overlengthening by a monopolar prosthesis was not found to be reliable for ruling out or quantifying overlengthening of the tested bipolar prosthesis. However, the use of the method to detect (rule in) overlengthening may be acceptable in certain circumstances. A reliable method for postoperative quantification of overlengthening by bipolar prostheses has still to be found.

The effect of short arm cast length on forearm rotation.

PURPOSE: To compare ranges of active forearm pronation and supination with subjects wearing short arm casts of different lengths. MATERIALS AND METHODS: Forty right-handed healthy volunteers (20 men and 20 women) with an average age of 39 years (range, 26-58 y) were recruited. A goniometer with a circular plate and a handle connected to the scale indicator was used to measure forearm pronation and supination without a cast and with 3 different lengths of short arm cast. All casts extended from just proximal to the volar and dorsal aspects of metacarpophalangeal joints, and continued to either 2.5 cm distal to elbow flexion crease or 5 cm distal to the elbow flexion crease, or to the proximal one-third position between the wrist flexion crease and the elbow flexion crease. RESULTS: Compared with no immobilization, the longest of the 3 constructs reduced active forearm rotation by 62%, whereas the cast to 5 cm from the elbow flexion crease reduced rotation to 50%, and the cast to the proximal one third of the way between the wrist and elbow flexion crease reduced rotation by 32%. Active forearm rotation was significantly dependent on cast length, and reductions in active forearm rotation were positively correlated with cast length. CONCLUSIONS: Limitation of active forearm rotation by a short arm cast is positively correlated with cast length. CLINICAL RELEVANCE: When a short arm cast is used to limit wrist motion and forearm rotation, it is better to extend it proximally but not to impinge on the antecubital fossa, where skin breakdown may occur.

The effect of distal radius translation in the coronal plane on forearm rotation: a cadaveric study of distal radius fractures.

PURPOSE: To determine the effect of lateral translation of the distal radius in the coronal plane on forearm rotation after distal radius fracture. METHODS: Ten fresh cadaveric limbs underwent distal radius osteotomy just proximal to the distal radial-ulnar joint to simulate an extra-articular distal radius fracture. We used an Agee Wrist Jack external fixator to create increasing magnitudes of distal fragment lateral translation in 2-mm increments. Forearm rotation was measured using a 3-dimensional camera at each magnitude of lateral translation. RESULTS: Total forearm rotation for the intact specimen and 2, 4, 6, and 8 mm (maximal) radial translations was 186° ± 53°, 188° ± 54°, 189° ± 55°, 190° ± 57°, and 193° ± 59°, respectively. There was no significant difference for any magnitude of radial translation. The average maximal radial translation possible before radioulnar abutment was 8 ± 0.5 mm. CONCLUSIONS: In this cadaveric model, translation of the distal radius fragment in the lateral direction had no effect on forearm rotation. CLINICAL RELEVANCE: At the level of the proximal border of the distal radioulnar joint, isolated distal radius translation does not significantly affect forearm rotation.

Comparison of the forearm rotation restriction capacities of four upper-extremity immobilization methods: there is no difference between single and double sugar tong splinting.

BACKGROUND: The aim of this study was to compare the effects of four different immobilization methods [single sugar tong splint (SSTS), double sugar tong splint (DSTS), short arm cast (SAC), and long arm cast (LAC)] commonly used for restricting forearm rotation in the upper extremity. METHODS: Forty healthy volunteers were included in the study. Dominant extremities were used for measurements. Basal pronation and supination of the forearm were measured with a custom-made goniometer, and the total rotation arc was calculated without any immobilization. Next, the measurements were repeated with the SAC, LAC, SSTS and DSTS. Each measurement was compared to the baseline value, and the percentage of rotation restriction was calculated. RESULTS: The most superior restriction rates were observed for the LAC (p = 0.00). No statistically significant difference was detected between the SSTS and DSTS in terms of the restriction of supination, pronation or the rotation arc (p values, 1.00, 0.18, and 0.50, respectively). Statistically significant differences were not detected between the SAC and the SSTS in any of the three parameters (p values, 0.25; 1.00; 1.00, respectively). When the SAC and DSTS were compared, while there was no significant difference between the two methods in pronation (p = 0.50), a statistically significant difference was detected in supination (p = 0.01) and in the total rotation arc (p = 0.03). CONCLUSION: The LAC provides superior results in restricting forearm rotation. The SAC and SSTS had similar effects on forearm rotation. The DSTS, which contains, in addition to the SSTS, a sugar tong portion above the elbow, does not provide additional rotational stability.

Biomechanical Stability of Diaphyseal Ulnar Shaft Fractures and Ulnar Shortening Osteotomies After Fixation.

BACKGROUND: To determine the amount of micromotion during forearm rotation after diaphyseal ulnar shaft fracture or osteotomy. METHODS: This was a biomechanical study using 7 paired-matched cadavers. The upper extremity was mounted in a custom rig and the forearm brought through full pronation and supination. A Hall effect sensor was placed at the fracture ends to measure micromotion for all tested conditions. There were 4 conditions tested: (1) intact ulnar shaft with plate to act as a control; (2) transverse fracture/osteotomy without stabilization; (3) fracture/osteotomy with cortical apposition stabilized with plate fixation; and (4) 50% comminuted fracture stabilized with plate. RESULTS: There was a significantly greater amount of fracture site motion in the fracture/osteotomy model without stabilization compared with all other tested conditions (P < .001, .0001, .0003, respectively). The fracture/osteotomy site with cortical apposition and the comminuted fracture models showed no statistically significant differences in the amount of micromotion compared with each another (P = .952) or compared with the intact ulnar shaft (P = .997, .889, respectively). CONCLUSIONS: There was no significant difference in the amount of motion between an intact ulnar shaft, an ulnar shaft fracture with cortical apposition stabilized with a plate, and a plated comminuted fracture. These findings may help surgeons decide on their type of postoperative immobilization in the setting of isolated ulnar shaft fractures or ulnar shaft osteotomies stabilized with plate fixation.

Length changes in the distal oblique band during forearm rotation measured using four-dimensional CT: an in vivo study.

Length change in the distal oblique band during forearm rotation was measured using four-dimensional CT in seven volunteers. There was no significant change in length, which provides more theoretical support for distal oblique band reinforcement for treatment of instability of the distal radioulnar joint.