Development of a novel murine femur fracture and fixation model.

BACKGROUND: Animal models have been used for decades to simulate human fractures in the laboratory setting. Fracture models in mice are attractive because they offer a high volume, relatively low-cost method of investigating fracture healing characteristics. We report on the development of a novel murine femur fracture model that is rapid, reproducible and inexpensive. METHODS: As part of a pilot study to investigate the effects of smoking on fracture healing, fifteen 35-43 g twelve-week old female CD-1 mice underwent a novel surgical protocol using direct visualization of femur fracture creation and fixation. Following surgery, mice were sacrificed at 14 days, 28 days and 42 days. After sacrifice, the femora were analyzed using MicroCT and histology to evaluate progression of healing. RESULTS: Of the 14 mice that survived the surgical procedure (one succumbed to a complication of anesthesia), two lost reduction and did not heal. Histology demonstrated at 14 days 44.1% (SD±2.9%) of callus composed of cartilage. At 28 days there was 19.0% (SD±3.4%) of callus composed of cartilage. At 42 days there was 8.4% (SD±2.6%) callus composed of cartilage (p < 0.005). MicroCT demonstrated that from 14 to 42 days the average callus volume decreased from 101.6 mm3 to 68.2 mm3 while the relative bone volume of callus increased from 14 to 42 days (15%-31%) (p = 0.068). CONCLUSIONS: Our novel fracture and fixation model is an effective, rapid, reproducible and inexpensive method to simulate a fracture in a laboratory setting. Additionally, our model reliably creates a reproducible progression of radiographic and histological bone healing.

What Patient-related Factors are Associated with an Increased Risk of Surgery in Patients with Stenosing Tenosynovitis? A Prospective Study.

BACKGROUND: Numerous patient-related risk factors have been identified as contributors to patient progression to operative treatment of stenosing tenosynovitis (STS). Identifying patients most at risk of undergoing surgery after receiving a corticosteroid injection would enable health care providers to identify patients most likely to benefit from nonsurgical treatment. QUESTIONS/PURPOSES: (1) What proportion of prospectively enrolled patients with a new diagnosis of STS did not require further intervention after a first, second, or third injection when offered up to three corticosteroid injections? (2) Which identifiable risk factors present at the initial evaluation in patients with STS are associated with the patient opting for surgical release after a trial of one, two, or three corticosteroid injections? METHODS: One hundred ninety-six patients with a presumed diagnosis of STS were evaluated between March 2014 and June 2015, and 160 patients with 186 affected fingers were prospectively enrolled after a new diagnosis of STS was made during the study period. STS was diagnosed by assessing for tenderness at the A1 pulley, passive or active triggering, and the absence of other confounding diagnoses. Only the affected finger received a corticosteroid injection, and these patients were followed up during the study period. Patients were followed for 2 years, and 135 of the 160 patients (84%) completed the final followup. Patients with recurrent symptoms were treated with up to three corticosteroid injections before undergoing A1 pulley release, although patients could elect to undergo surgery at any time. Bivariate comparisons and a multivariate logistic regression analysis were used for independent fingers (one per participant) to identify independent variables associated with progression to surgery after injection. The time between treatments (between injection and subsequent injection or between injection and surgery) for those with recurrent symptoms was also calculated. Information collected from the last time the patient could be contacted was carried forward in the analysis for all 160 patients. RESULTS: No further treatment was sought after the first, second, and third injections by 81 of 160 (51%), 16 of 45 (37%), and three of 10 patients (30%), respectively; 100 of 160 patients (63%) did not pursue further intervention. After the first, second, and third injections, 36 of 160 patients (23%), 17 of 43 patients (40%), and seven of 10 of patients, respectively, did not respond to treatment. After controlling for 21 potentially confounding patient- and disease-related variables, we found that only two risk factors at the initial presentation were protective against eventual progression to surgery: osteoarthritis in the fingers (odds ratio [OR], 0.26 [95% CI, 0.085-0.786]; p = 0.017) and a longer duration of symptoms (OR, 0.58 [95% CI, 0.38-0.89]; p = 0.012). There was no association between progression to surgery and hand dominance, finger type (thumb or other), whether the patient had diabetes, or whether the affected finger was one of multiple affected fingers. Patients who presented again for intervention (injection or surgery) did so at a mean of 153 ± 94 days. CONCLUSIONS: Although patients should be counseled that their risk of progressing to surgery after an initial corticosteroid injection is lower than for subsequently administered injections for recurrent symptoms, nonoperative treatment should not be bypassed for patients with any of the studied risk factors. LEVEL OF EVIDENCE: Level II, therapeutic study.

Fixation Strength in Full and Limited Fixation of Osteoporotic Distal Radius Fractures.

BACKGROUND: The purpose of this investigation is to determine whether osteoporotic intra-articular distal radius fractures surgically treated by filling all 7 distal screws of a volar plate will have a higher load to failure than those treated by filling only 4 distal screws. METHODS: Ten matched pairs of fresh frozen cadaveric forearms were randomized within each pair to be treated by using either all 7 of the distal holes of a volar plate or only 4 distal screws. The distal radius fixation was performed with unicortical screws going to but not through the dorsal cortex, and the most distal screws were placed within 4 mm of the joint surface. An AO C2 type fracture was then created. All specimens were tested cyclically, with an axial load of 60 N, at 3 Hz for 1000 cycles to simulate early postoperative motion. All specimens were subsequently tested to mechanical failure. RESULTS: There were no failures in either group during cyclic testing. There was no difference detected between groups for mean stiffness, yield load, peak load, or load to clinical failure. In both groups, the yield load, peak load, and load to clinical failure were higher than the 60- to 100-N forces encountered during postoperative rehabilitation. CONCLUSIONS: There was no difference detected between osteoporotic intra-articular distal radius fractures treated by utilizing all 7 of the distal screws of a volar plate compared with those treated with only 4 distal screws.

Relative Contributions of the Midcarpal and Radiocarpal Joints to Dart-Thrower's Motion at the Wrist.

PURPOSE: To identify the relative contributions of the radiocarpal (RC) and midcarpal (MC) joints to dart-thrower's motion (DTM) of the wrist. METHODS: Six cadaveric upper extremities were fixed to a custom-designed loading jig allowing for pure moment-rotation analysis in 24 different directions of wrist motion. Each specimen was tested in 3 states: intact, simulated radiocarpal fusion (sRCF) and simulated pancarpal fusion (sPCF). Moments of ± 1.5 Nm were applied at each of 24 directions for each state and the resulting wrist rotation recorded. Data from each specimen were reduced to compute the range of motion (ROM) envelopes and the orientation of the ROM for the 3 different states. RESULTS: The ROM was significantly decreased in the sRCF and sPCF groups compared with the intact group in the directions of the pure extension, radial extension, ulnar flexion, and ulnar deviation. No significant difference in ROM was detected between the sRCF and sPCF groups in any direction. The ROM envelopes for the intact, sRCF, and sPCF groups were all oriented obliquely to the axis of pure wrist flexion-extension near a path of ulnar flexion-radial extension, consistent with prior reports on DTM. CONCLUSIONS: Although both simulated fusion types decreased ROM compared with the intact wrist, the principal direction of wrist motion along the path of DTM was not significantly altered by simulated RCF or PCF. CLINICAL RELEVANCE: These findings suggest that the RC and MC joints can each contribute to a similar mechanical axis of motion located along the path of DTM when the other joint has been eliminated via fusion. Surgical options such as partial wrist fusions may maintain the native wrist's mechanical axis if either the RC or the MC joint is preserved, despite significant reduction in overall ROM.

Three-Dimensional Carpal Kinematics after Carpal Tunnel Release.

BACKGROUND: Carpal tunnel release (CTR) has been shown to change carpal arch morphology. However, the effect of CTR on the three-dimensional kinematics of the carpal bones has not been demonstrated. PURPOSE: This study examined whether release of the transverse carpal ligament (TCL) would alter the three-dimensional kinematics of the carpus, specifically the bony attachments of the TCL. METHODS: The in vitro kinematics of the carpus was studied in five fresh-frozen cadaveric wrists before and after CTR using three-dimensional computed tomography. The specimens were evaluated in three positions: neutral, 60 degrees of flexion, and 60 degrees of extension. RESULTS: The data indicate that carpal arch width increases significantly in all positions after CTR as measured between the trapezium and hamate. Second, the trapezium-hamate distance increases in both a translational and rotational component after CTR. Additionally, the pisiform rotates away from the triquetrum after CTR. CONCLUSIONS: Carpal kinematics is significantly altered with a CTR, especially on the ulnar side of the wrist. CLINICAL RELEVANCE: Although the kinematic changes are small, they may be clinically significant and potentially responsible for pillar pain or postoperative loss of grip strength.

The effects of distal interlocking screws on torsional stability in three-part intertrochanteric hip fractures.

OBJECTIVE: Many surgeons currently use long cephomedullary nails for the treatment of intertrochanteric fractures. The optimal indications for deploying distal interlocks are still debatable. This study examined the torsional biomechanical properties of 3-part intertrochanteric femur fractures in a cadaveric bone model using two different distal fixation strategies, an unlocked long cephalomedullary nail versus a dynamically locked nail. Our hypothesis is that a long cephalomedullary nail does not require distal locking fixation when used for treatment of a 3-part intertrochanteric fracture. METHODS: Five matched pairs of cadaveric femora were randomly assigned to one of two distal fixation treatment groups; a single distal interlock screw placed in the dynamic orientation or no distal fixation. A 3-part intertrochanteric fracture was produced. Specimens were potted and mounted in a double gimbal fixture facilitating unconstrained motion in the sagittal and coronal planes. Specimens were cyclically loaded dynamically in both internal and external rotation. Range of motion, internal and external rotation stiffness, torsion stiffness, torsion yield and ultimate torsion magnitude were calculated. RESULTS: The samples instrumented with a distal locking screw reported statistically greater external rotational stiffness than the unlocked samples in nondestructive testing. The results of the destructive data demonstrated no statistical difference between the locked and unlocked group with regard to yield torque (p = 0.282), peak torque (p = 0.340), stiffness (p = 0.220), displacement at yield torque (p = 0.0605), and displacement at peak torque (p = 0.280). CONCLUSION: Distal locking of a long cephalomedullary nail increases the stiffness of the nail-femur construct in a 3-part biomechanical fracture model. However, our testing illustrates that an unlocked construct will tolerate at least equal stress before catastrophic failure in a torsional loading model.

Divergent elbow dislocation and risk of compartment syndrome.

BACKGROUND: Divergent pediatric elbow dislocations are very rare injuries. CASE: An eight-year-old boy presented to the emergency department with elbow pain after a fall. On examination his elbow was swollen; skin and neurovascular function were intact. Radiographs demonstrated a divergent elbow dislocation. After successful closed reduction under sedation, the arm was casted; gentle motion was initiated at three weeks. At four months, the patient had full strength, no symptoms, and nearly full range of motion. INTERPRETATION: The literature on the treatment of this injury is limited because of its rarity. We present a case of successful nonoperative management. The return of this patient for compressive symptoms should serve as a reminder that these injuries may be at high risk for compartment syndrome, possibly due to the high level of soft tissue disruption.

Cobalt toxicity after revision to a metal-on-polyethylene total hip arthroplasty for fracture of ceramic acetabular component.

Cobalt metallosis after revision metal-on-polyethylene total hip arthroplasty for catastrophic failure of ceramic components is uncommon but a potentially devastating complication. Common findings associated with heavy metal toxicity include cardiomyopathy, hypothyroidism, skin rashes, visual disturbances, hearing changes, polycythemia, weakness, fatigue, cognitive deterioration, and neuropathy. We report a case of a 57-year-old woman who presented with complaints of progressively worsening hip pain, fatigue, memory loss, lower extremity sensory loss, persistent tachycardia, and ocular changes 5 years after synovectomy and revision of a failed ceramic-on-ceramic total hip arthroplasty to metal-on-polyethylene components. A cobalt level of 788.1 ppb and chromium level of 140 ppb were found on presentation and subsequently decreased to 468.8 ppb and 105.9 ppb, respectively, 2 weeks after revision to a ceramic-on-polyethylene total hip arthroplasty. Improvement of symptoms accompanied this decrease in cobalt and chromium levels. Revision of failed ceramic arthroplasties with later-generation ceramics to avoid this potential complication is recommended.

Delayed Erosion of a Pelvic Reconstruction Plate into the Bladder Causing Recurrent Urinary Tract Infections: A Case Report.

CASE: A forty-seven-year-old woman presented with recurrent urinary tract infections eleven years after open fixation of a pelvic ring injury. Cystoscopy revealed that the pelvic reconstruction plate had eroded into the bladder, likely the source of the recurrent infections. Following removal of the involved pelvic hardware and repair of the bladder, the patient had no further urinary tract infections. CONCLUSION: Operative fixation of osseous pelvic injuries places metal implants in proximity to the bladder. Late erosion of hardware into the bladder can occur. A low threshold for urological work-up should be maintained for recurrent genitourinary symptoms in these patients.

Initial management of ankle fractures in the overweight and obese: the providence pinch.

BACKGROUND: Obese and overweight people have higher rates of ankle injury, particularly operative ankle fractures. The initial management of unstable ankle fractures includes closed reduction and splinting to limit soft tissue injury and articular cartilage damage until definitive operative fixation can be performed. Adequate reduction can be more difficult in the obese patient due to the weight and additional padding provided by the larger soft tissue envelope. DISCUSSION: A novel technique, described herein by the authors, may be useful in obtaining a suitable reduction of the ankle in the initial management of unstable ankle fractures in the overweight and obese. CONCLUSIONS: Obese patients have unique musculoskeletal injury profiles and special considerations in their management. The authors have found this technique useful in the management of their ankle fractures.

Nerve compression syndromes of the upper extremity: diagnosis, treatment, and rehabilitation.

Nerve compression syndromes of the upper extremity, including carpal tunnel syndrome, cubital tunnel syndrome, posterior interosseous syndrome and radial tunnel syndrome, are common in the general population. Diagnosis is made based on patient complaint and history as well as specific exam and study findings. Treatment options include various operative and nonoperative modalities, both of which include aspects of hand therapy and rehabilitation.