Anatomic and Biomechanical Study of Thumb Carpometacarpal Dislocations: A Laboratory Study.

BACKGROUND: No previous study recreating an isolated thumb carpometacarpal (CMC) dislocation with or without suture augmentation has been performed in the laboratory. This investigation aimed to evaluate the mechanism and ligamentous complex of isolated thumb CMC dislocations. METHODS: Biomechanical analysis was performed in 10 cadaveric specimens. A posteriorly directed force or axial loading with hyperflexion through the CMC joint was applied. Load was applied at a rate of 1 mm/s until posterior CMC dislocation was achieved. Maximum load, displacement under nominal loading, stiffness, and mode of failure were recorded. The native ligament was repaired, augmented with high-tensile suture, and testing was repeated. RESULTS: Posteriorly directed force produced posterior CMC dislocations, while axial loading and hyperflexion through the CMC joint caused fractures. Load-to-failure of the native CMC joint was 217.76 N (SD = 66.03). Stiffness of the ligamentous complex on average was 18.86 N/mm (SD = 8.83). Mean load-to-failure after repair with suture augmentation was 94.62 N (SD = 39.77), with average stiffness of 8.21 N/mm (SD = 3.06). The native ligament was noted to have greater stiffness (P = .002) and greater load-to-failure (P = .0001) than repair with suture augmentation. Maximum displacement-to-failure of the native ligament was 14.5 mm compared with repair with suture augmentation 11.9 mm (P = .068). CONCLUSION: Isolated CMC dislocation was achieved with a posteriorly directed force rather than hyperflexion of the joint. Ultimate failure load of the repaired ligaments with suture augmentation was about half of that of the native ligaments. Further research into this technique is warranted.

Systematic Review of Ligament Reconstruction of Traumatic Isolated Thumb Carpometacarpal Joint Dislocation.

INTRODUCTION: Thumb carpometacarpal (CMC) joint dislocations are rare with minimal agreement on surgical management. The dorsoradial ligament (DRL) is the primary joint stabilizer but has not historically been reconstructed. We hypothesize that the reported reconstruction of first CMC joint dislocations primarily uses the flexor carpi radialis (FCR) without collective agreement on a surgical technique. METHODS: A systematic review of the PubMed database from 1996 to 2022 was done. Keywords were "thumb dislocation," "thumb carpometacarpal dislocation," and "carpometacarpal joint ligament repair." Inclusion criteria included isolated, unstable thumb CMC dislocations with reconstruction. The Preferred Reporting Items for Systematic Reviews and Meta Analyses guidelines were used. RESULTS: Four hundred thirty-seven records were identified, and nine met inclusion criteria. Two articles were cohort studies, and seven were case reports. Thirty-seven patients were included, and 26 patients had reconstruction with tendonous autograft. Twenty-five (96.2%) used the FCR and 1 (3.9%) from the palmaris longus. Three patients had reconstruction with a suture anchor. Surgical techniques varied between studies. DISCUSSION: The recommendation of the authors recreates the DRL during autograft repair. Current repair techniques that recreate the DRL use the FCR, but quantitative comparisons of tendonous autografts or suture anchors have not been done.

Management of thumb carpometacarpal joint dislocations: A systematic review.

Although rare, thumb Carpometacarpal (CMC) joint dislocations can have significant complications which impact hand function. Optimal management is crucial in restoring pinch and grasp strength, but no agreement exists regarding treatment due to a paucity of literature on this subject. Systematic review was conducted involving non-operative and operative management of the CMC joint. 15 articles with a total of 60 thumbs were evaluated from published literature. 12/60 thumbs with isolated CMC joint dislocations were treated with closed reduction, with 4 cases needing additional ligament repair due to joint instability post-reduction. 51/60 of the isolated CMC joint dislocations had ligament reconstruction, with flexor carpi radialis tendon autograft (29/51) as the most popular option. 60/60 patients regained full function and stability of the CMC joint with significant pain relief. Although good surgical outcomes have been achieved, long term clinical outcome reporting is needed to develop a standardized approach to treatment.

Return to Yoga Rates Are High After Volar Plating of Distal Radius Fractures.

Background: Yoga is a popular activity involving extreme wrist positioning and extension loading. Our purpose was to quantify the prevalence of preoperative yoga participation and characterize subsequent ability to return to yoga in patients undergoing volar locked plating of distal radius fractures. Methods: We retrospectively reviewed all cases of distal radius open reduction internal fixation between August 2015 and March 2017. Patients were included if they were treated with volar locked plating and if they participated in yoga on a regular basis preoperatively. Patients were contacted at a minimum of 1 year postoperatively and surveyed about yoga participation. Results: A total of 149 patients who underwent distal radius volar plating were surveyed. Thirty-one patients (32 procedures, 20.8% of surveyed patients) participated in yoga on a regular basis preoperatively. Overall, 90.3% returned to yoga in some capacity. Mean times to return to yoga in any capacity, with weight-bearing, and in a "steady state" were 5.7, 7.4, and 10.0 months, respectively. Of patients who resumed yoga, 65.5% returned to the same or better level of yoga. Satisfaction with participation in yoga was 8.9 (out of 10). Conclusions: We found a relatively high yoga participation rate in patients undergoing distal radius fracture fixation, suggesting the need to be able to effectively counsel these patients. Our results demonstrate a high rate of return to yoga, although approximately one-third of patients experienced a decreased level of participation. Surgeons can use this information to set appropriate expectations.

Femoral Iatrogenic Subtrochanteric Fatigue Fracture Risk is not Increased by Placing Drill Holes Below the Level of the Lesser Trochanter.

BACKGROUND: Iatrogenic subtrochanteric fractures of the femur can occur postoperatively following placement of screws in the lateral femoral cortex. Drilling holes below the lesser trochanter is generally avoided to prevent fatigue failure; however, there is little biomechanical evidence to support this recommendation. We hypothesized that hole placement below the level of the lesser trochanter will not accelerate fatigue failure compared to holes at the level of the lesser trochanter. METHODS: Twelve matched-pairs of male fresh-frozen cadaveric femurs were used for biomechanical testing. A single screw hole was drilled through the lateral femoral cortex either at the level of the lesser trochanter (proximal-hole group) or below the lesser trochanter (distal-hole group). Each femur was cycled to failure using a physiologically-relevant loading model. Paired t-test was used to evaluate for a difference in cycles to failure between groups. RESULTS: There was no statistical difference in cycles to failure between the groups with the hole drilled at or below the lesser trochanter. CONCLUSIONS: The traditional recommendation to avoid drilling holes below the level of the lesser trochanter is based mainly on experience and case reports in the literature. The results of this study indicate that placing holes below the level of the lesser trochanter, in and of itself, may not pose any additional risk of fracture. Other important factors need to be considered, such as tapering of the lateral femoral cortex. CLINICAL RELEVANCE: There are often situations where the patient's anatomy and facture pattern is more conducive to placing a screw distal to the lesser trochanter. This study may allow surgeons greater flexibility in placing screws more distally in the lateral femoral cortex by demonstrating the safety of doing so, at least in the population studied.

Biomechanical evaluation of a novel suturing scheme for grafting load-bearing collagen scaffolds for rotator cuff repair.

BACKGROUND: Currently, there are no well-established suture protocols to attach fully load-bearing scaffolds which span tendon defects between bone and muscle for repair of critical sized tendon tears. Methods to attach load-bearing tissue repair scaffolds could enable functional repair of tendon injuries. METHODS: Sixteen rabbit shoulders were dissected (New Zealand white rabbits, 1yr. old, female) to isolate the humeral-infraspinatus muscle complex. A unique suture technique was developed to allow for a 5mm segmental defect in infraspinatus tendon to be replaced with a mechanically strong bioscaffold woven from pure collagen threads. The suturing pattern resulted in a fully load-bearing scaffold. The tensile stiffness and strength of scaffold repair were compared with intact infraspinatus and regular direct repair. FINDINGS: The failure load and displacement at failure of the scaffold repair group were 59.9N (standard deviation, SD=10.7) and 10.3mm (SD=2.9), respectively and matched those obtained by direct repair group which were 57.5N (SD=15.3) and 8.6mm (SD=1.5), (p>0.05). Failure load, displacement at failure and stiffness of both of the repair groups were half of the intact infraspinatus shoulder group. INTERPRETATION: With the developed suture technique, scaffold repair showed similar failure load, displacement at failure and stiffness to the direct repair. This novel suturing pattern and the mechanical robustness of the scaffold at time zero indicates that the proposed model is mechanically viable for future in vivo studies which has a higher potential to translate into clinical uses.

A fatigue loading model for investigation of iatrogenic subtrochanteric fractures of the femur.

BACKGROUND: Biomechanics of iatrogenic subtrochanteric femur fractures have been examined. Previously-described loading models employed monotonic loading on the femoral head, which is limited in emulating physiological features. We hypothesize that cyclic loading combined with the engagement of abductor forces will reliably cause iatrogenic subtrochanteric fractures. METHODS: Finite element analysis determined the effects of adding the abductor muscle forces to the hip contact force around holes located in the lateral femoral cortex. Finite element analysis predictions were validated by strain gage measurements using Sawbones™ femurs (Pacific Research Laboratories, Inc., Vashon, Washington, USA) with or without abductor muscle forces. The newly developed physiologically-relevant loading model was tested on cadaveric femurs (N=8) under cyclic loading until failure. FINDINGS: Finite element analysis showed the addition of the abductor muscle forces increased the maximum surface cortical strain by 107% and the strain energy density by 332% at the lateral femoral cortex. Strain gages detected a 72.9% increase in lateral cortical strain using the combined loading model. The cyclic, combined loading led to subtrochanteric fractures through the drill hole in all cadaveric femurs. INTERPRETATION: Finite element analysis simulations, strain gage measurements, and cyclic loading of fresh-frozen femurs indicate the inclusion of abductor forces increases the stress and strain at the proximal-lateral femoral cortex. Furthermore, a cyclic loading model that incorporates a hip contact force and abductor muscles force creates the clinically encountered subtrochanteric fractures in vitro. This physiologically-relevant loading model may be used to further study iatrogenic subtrochanteric femur fractures.

A biomechanical analysis of the native coracoclavicular ligaments and their influence on a new reconstruction using a coracoid tunnel and free tendon graft.

PURPOSE: To understand and characterize the kinematic properties of the 2 coracoclavicular ligaments and to evaluate the biomechanical performance of a new 3-tunnel reconstruction of the coracoclavicular ligaments by use of a free tendon graft. METHODS: Ten fresh-frozen cadaveric shoulders were tested. The kinematics and in situ forces of the coracoclavicular ligaments were tested with a robotic testing system. Kinematics of the shoulder in the intact state, in the sectioned state, and finally, after a coracoclavicular reconstruction and a coracoclavicular sling reconstruction were evaluated. RESULTS: The conoid had higher in situ forces during anterior and superior loading of the clavicle when compared with the trapezoid ligament, whereas the trapezoid ligament had higher in situ forces during posterior loading. Sectioning the trapezoid ligament significantly increased translation of the clavicle in the posterior direction, whereas sectioning the conoid ligament significantly increased superior translation. When we compared the 2 reconstruction techniques, the coracoid tunnel reconstruction was superior in controlling anterior translation whereas the coracoclavicular sling reconstruction was inferior because of anterior displacement of the graft. There was no significant difference in posterior or superior translation between either reconstruction technique. CONCLUSIONS: The trapezoid and conoid ligaments have unique functions in normal shoulder kinematics because of their anatomic attachments. By more faithfully restoring these insertion sites on the clavicle and controlling motion of the graft on the coracoid, the 3-tunnel reconstruction technique more closely restores native shoulder kinematics than the coracoclavicular sling technique. CLINICAL RELEVANCE: Understanding the unique roles of the conoid and trapezoid bundles of the coracoclavicular ligament may improve surgical techniques in the management of acromioclavicular joint injuries. The reconstructive technique presented more faithfully restores normal kinematics and forces across the acromioclavicular joint than the coracoclavicular sling technique.

Comparative kinematic evaluation of all-inside single-bundle and double-bundle anterior cruciate ligament reconstruction: a biomechanical study.

BACKGROUND: The efficacy of single-bundle versus double-bundle ACL reconstruction in improving knee stability has been widely discussed. The biomechanics of all-inside double-bundle ACL reconstructions have not been evaluated. HYPOTHESIS: An anatomic all-inside double-bundle ACL reconstruction will more effectively restore native knee kinematics in vitro, especially rotational stability, when compared with an all-inside single-bundle ACL reconstruction. STUDY DESIGN: Controlled laboratory study. METHODS: Seven pairs of fresh-frozen cadaveric human knees were used. Knees were tested using 88 N of force for anterior and posterior drawers, 5 N.m internal and external rotation moments, 10 N.m valgus and varus moments, and coupled 5 N.m internal rotation and 10 N.m valgus moments to simulate a pivot shift at 0 degrees , 20 degrees , 30 degrees , 60 degrees , and 90 degrees of knee flexion. Motion of the knee in response to external loading was measured with a Polhemus electromagnetic tracking system. Knees were first tested in the intact state, with either the anteromedial or posterolateral bundle cut, and then with both bundles cut. Subsequently, 7 single-bundle and 7 double-bundle all-inside ACL reconstructions were performed. RESULTS: Both single- and double-bundle all-inside ACL reconstructions restored knee kinematics for posterior drawer, varus/valgus rotation, and internal/external rotation motions. After single-bundle all-inside ACL reconstruction, anterior translation during the simulated pivot-shift test was significantly higher compared with the intact state at 20 degrees , 30 degrees , and 60 degrees of flexion. There was no significant difference between the double-bundle all-inside ACL reconstruction and the intact knee during a simulated pivot shift. Conclusion We found that an all-inside double-bundle ACL reconstruction demonstrated significant improvement in restoring normal rotational knee motion during simulated pivot-shift testing compared with single-bundle ACL reconstructions in vitro, with no significant differences in other knee loading conditions. CLINICAL RELEVANCE: All-inside double-bundle ACL reconstruction may provide advantages over single-bundle ACL reconstruction for rotational knee stability.

Rotational knee laxity: reliability of a simple measurement device in vivo.

BACKGROUND: Double bundle ACL reconstruction has been demonstrated to decrease rotational knee laxity. However, there is no simple, commercially-available device to measure knee rotation. The investigators developed a simple, non-invasive device to measure knee rotation. In conjunction with a rigid boot to rotate the tibia and a force/moment sensor to allow precise determination of torque about the knee, a magnetic tracking system measures the axial rotation of the tibia with respect to the femur. This device has been shown to have acceptable levels of test re-test reliability to measure knee rotation in cadaveric knees. METHODS: The objective of this study was to determine reliability of the device in measuring knee rotation of human subjects. Specifically, the intra-tester reliability within a single testing session, test-retest reliability between two testing sessions, and inter-tester reliability were assessed for 11 male subjects with normal knees. RESULTS: The 95% confidence interval for rotation was less than 5 degrees for intra-tester, test-retest, and inter-tester reliability, and the standard error of measurement for the differences between left and right knees was found to be less than 3 degrees . CONCLUSION: It was found that the knee rotation measurements obtained with this device have acceptable limits of reliability for clinical use and interpretation.

Development of a simple device for measurement of rotational knee laxity.

The goal of this study was to develop a new device for the measurement of rotational knee laxity and to measure intra-observer and inter-observer reliability in a cadaveric study. An array of established tools was utilized to design the device with a basis that consists of an Aircast Foam Walkertrade mark boot. A load cell was attached to the boot with a handle bar for application of moments about the knee. An electromagnetic tracking system was used to record the motion of the tibia with respect to the femur. The total arc of motion ranged from 23 degrees at full extension to 46 degrees at 90 degrees of knee flexion. The intra-tester ICCs ranged from 0.94 to 0.99. The ICC for inter-tester reliability ranged from 0.95 to 0.99. In summary, the new device for measurement of rotational knee laxity is simple, reliable, and can be used in a non-invasive fashion in the office or surgical suite document clinical outcome in terms of rotational knee laxity.