Internal joint stabilizer for varus posteromedial rotatory instability of the elbow.

BACKGROUND: Management of varus posteromedial rotatory instability (VPMRI) of the elbow presents a challenging problem, sometimes requiring supplemental external fixation or ulnohumeral cross-pinning. A relatively new treatment adjunct for posterolateral rotatory instability of the elbow has become available with the development of the internal joint stabilizer (IJS) implant. However, this has not been studied for VPMRI because the implant is thought to be ineffective at treating this instability when placed in the usual manner on the lateral side of the elbow. We hypothesize that modifying the IJS technique to place the implant medially will make it as effective as external fixation at preventing VPMRI. METHODS: Nine whole-arm cadaveric specimens were tested on a rig that allowed for gravity stress of the elbow at 60° of abduction. Intact specimens (INT) were tested to find the baseline stability with all structures intact. Then, O'Driscoll type 2-subtype III coronoid fractures were created with a microsagittal saw, and these same specimens were again tested without any fixation (WAF), with a static lateral external fixator (SLEF), and with a medially placed IJS (MIJS). The method for medial IJS placement is detailed within. RESULTS: The WAF specimens were significantly more unstable than the INT, SLEF, and MIJS groups (P < .001). There was no difference in stability between the INT and the SLEF (P = .59) or MIJS group (P = .21). CONCLUSION: In this cadaveric model, a medially placed IJS was as effective as an SLEF at maintaining elbow stability in a coronoid-deficient elbow. This technique allows for early elbow range of motion, with no external hardware, and may eliminate the complications associated with external fixation or ulnohumeral cross-pinning.

Effects of immobilization angle on tendon healing after achilles rupture in a rat model.

Conservative (non-operative) treatment of Achilles tendon ruptures is a common alternative to operative treatment. Following rupture, ankle immobilization in plantarflexion is thought to aid healing by restoring tendon end-to-end apposition. However, early activity may improve limb function, challenging the role of immobilization position on tendon healing, as it may affect loading across the injury site. This study investigated the effects of ankle immobilization angle in a rat model of Achilles tendon rupture. We hypothesized that manipulating the ankle from full plantarflexion into a more dorsiflexed position during the immobilization period would result in superior hindlimb function and tendon properties, but that prolonged casting in dorsiflexion would result in inferior outcomes. After Achilles tendon transection, animals were randomized into eight immobilization groups ranging from full plantarflexion (160°) to mid-point (90°) to full dorsiflexion (20°), with or without angle manipulation. Tendon properties and ankle function were influenced by ankle immobilization position and time. Tendon lengthening occurred after 1 week at 20° compared to more plantarflexed angles, and was associated with loss of propulsion force. Dorsiflexing the ankle during immobilization from 160° to 90° produced a stiffer, more aligned tendon, but did not lead to functional changes compared to immobilization at 160°. Although more dorsiflexed immobilization can enhance tissue properties and function of healing Achilles tendon following rupture, full dorsiflexion creates significant tendon elongation regardless of application time. This study suggests that the use of moderate plantarflexion and earlier return to activity can provide improved clinical outcomes. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Tendon healing affects the multiscale mechanical, structural and compositional response of tendon to quasi-static tensile loading.

Tendon experiences a variety of multiscale changes to its extracellular matrix during mechanical loading at the fascicle, fibre and fibril levels. For example, tensile loading of tendon increases its stiffness, with organization of collagen fibres, and increases cell strain in the direction of loading. Although applied macroscale strains correlate to cell and nuclear strains in uninjured tendon, the multiscale response during tendon healing remains unknown and may affect cell mechanosensing and response. Therefore, this study evaluated multiscale structure-function mechanisms in response to quasi-static tensile loading in uninjured and healing tendons. We found that tendon healing affected the macroscale mechanical and structural response to mechanical loading, evidenced by decreases in strain stiffening and collagen fibre realignment. At the micro- and nanoscales, healing resulted in increased collagen fibre disorganization, nuclear disorganization, decreased change in nuclear aspect ratio with loading, and decreased indentation modulus compared to uninjured tendons. Taken together, this work supports a new concept of nuclear strain transfer attenuation during tendon healing and identifies several multiscale properties that may contribute. Our work also provides benchmarks for the biomechanical microenvironments that tendon cells may experience following cell delivery therapies.

Benign heart murmurs as a predictor for complications following total joint arthroplasty.

BACKGROUND: There is scant literature examining the predictive role of heart murmurs in the absence of suspected structural heart disease on complications of non-cardiac surgery. We hypothesize the detection of heart murmurs in the absence of structural heart disease will help identify patients at risk for complications following total joint arthroplasty (TJA) surgery. METHOD: This was a prospective cohort of patients undergoing TJA over a twenty-month period. The study was performed at a single academic institution with four subspecialty surgeons. Patients undergoing primary TJA who were over eighteen years old, gave informed consent, and had adequate documentation were included in the study. Patients with a preoperative murmur or a newly discovered postoperative murmur were compared against patients with no murmur. Surgery-related complications, performance with physical therapy, and discharge to a non-home facility were measured in each group. FINDINGS: 345 (63%) eligible patients were included. 20 (5.8%) patients had a documented preoperative murmur and 36 (10.4%) patients had a new postoperative murmur. No patient had concern for major structural heart disease. Preoperative murmurs independently predicted development of acute kidney injury (OR 7.729, p < 0.001; RR 1.36). Preoperative murmurs also predicted likelihood to be discharged to a non-home facility (OR 2.97, p = 0.03; RR 1.87). New postoperative murmurs independently correlated with decreased performance with physical therapy (OR 0.466, p = 0.045; RR 0.664). INTERPRETATION: Detection of heart murmurs both preoperatively and postoperatively is a low cost strategy to identify post-TJA surgical patients at risk for postoperative acute kidney injury, decreased physical performance, and discharge to non-home facilities. These patients may benefit from early fluid resuscitation and renally-dosed post-operative medications.

Mechanical, histological, and functional properties remain inferior in conservatively treated Achilles tendons in rodents: Long term evaluation.

Conservative treatment (non-operative) of Achilles tendon ruptures is suggested to produce equivalent capacity for return to function; however, long term results and the role of return to activity (RTA) for this treatment paradigm remain unclear. Therefore, the objective of this study was to evaluate the long term response of conservatively treated Achilles tendons in rodents with varied RTA. Sprague Dawley rats (n=32) received unilateral blunt transection of the Achilles tendon followed by randomization into groups that returned to activity after 1-week (RTA1) or 3-weeks (RTA3) of limb casting in plantarflexion, before being euthanized at 16-weeks post-injury. Uninjured age-matched control animals were used as a control group (n=10). Limb function, passive joint mechanics, tendon properties (mechanical, histological), and muscle properties (histological, immunohistochemical) were evaluated. Results showed that although hindlimb ground reaction forces and range of motion returned to baseline levels by 16-weeks post-injury regardless of RTA, ankle joint stiffness remained altered. RTA1 and RTA3 groups both exhibited no differences in fatigue properties; however, the secant modulus, hysteresis, and laxity were inferior compared to uninjured age-matched control tendons. Despite these changes, tendons 16-weeks post-injury achieved secant stiffness levels of uninjured tendons. RTA1 and RTA3 groups had no differences in histological properties, but had higher cell numbers compared to control tendons. No changes in gastrocnemius fiber size or type in the superficial or deep regions were detected, except for type 2x fiber fraction. Together, this work highlights RTA-dependent deficits in limb function and tissue-level properties in long-term Achilles tendon and muscle healing.

Postinjury biomechanics of Achilles tendon vary by sex and hormone status.

Achilles tendon ruptures are common injuries. Sex differences are present in mechanical properties of uninjured Achilles tendon, but it remains unknown if these differences extend to tendon healing. We hypothesized that ovariectomized females (OVX) and males would exhibit inferior postinjury tendon properties compared with females. Male, female, and OVX Sprague-Dawley rats (n = 32/group) underwent acclimation and treadmill training before blunt transection of the Achilles tendon midsubstance. Injured hindlimbs were immobilized for 1 wk, followed by gradual return to activity and assessment of active and passive hindlimb function. Animals were euthanized at 3 or 6 wk postinjury to assess tendon structure, mechanics, and composition. Passive ankle stiffness and range of motion were superior in females at 3 wk; however, by 6 wk, passive and active function were similar in males and females but remained inferior in OVX. At 6 wk, female tendons had greater normalized secant modulus, viscoelastic behavior, and laxity compared with males. Normalized secant modulus, cross-sectional area and tendon glycosaminoglycan composition were inferior in OVX compared with females at 6 wk. Total fatigue cycles until tendon failure were similar among groups. Postinjury muscle fiber size was better preserved in females compared with males, and females had greater collagen III at the tendon injury site compared with males at 6 wk. Despite male and female Achilles tendons withstanding similar durations of fatigue loading, early passive hindlimb function and tendon mechanical properties, including secant modulus, suggest superior healing in females. Ovarian hormone loss was associated with inferior Achilles tendon healing.

Adult-acquired flatfoot deformity and age-related differences in foot and ankle kinematics during the single-limb heel-rise test.

STUDY DESIGN: Cross-sectional laboratory study. OBJECTIVE: To compare single-limb heel-rise performance and foot-ankle kinematics between persons with stage 2 adult-acquired flat foot deformity (AAFD) and healthy controls. BACKGROUND: The inability to perform a single-limb heel rise is considered a positive functional diagnostic test for AAFD. However, which foot motions contribute to poor performance of this task are not known. METHODS: Fifty individuals participated in this study, 20 with stage 2 AAFD (mean ± SD age, 57.6 ± 11.3 years), and 15 older participants (age, 56.8 ± 5.3 years) and 15 younger participants (age, 22.2 ± 2.4 years) without AAFD as control groups. Forefoot (sagittal plane) and rear foot (sagittal and frontal planes) kinematics were collected using a 3-D motion analysis system. Heel-rise performance (heel height) and kinematics (joint angles, excursions) were evaluated. One-way and 2-way analyses of variance were used to examine differences in heel-rise performance and kinematics between groups. RESULTS: Individuals with AAFD and older controls demonstrated lower heel-rise height than those in the younger control group (P<.001). Persons with AAFD demonstrated higher degrees of first metatarsal dorsiflexion (P<.001), lower ankle plantar flexion (P<.001), and higher subtalar eversion (P = .027) than those in the older control group. Persons with AAFD demonstrated lower ankle excursion (P<.001) and first metatarsal excursion (P<.001) than those in the older control group, but no difference in subtalar excursion (P = .771). CONCLUSION: Persons with stage 2 AAFD did not achieve sufficient heel height during a single-leg heel rise. Both forefoot and rear foot kinematics in the sagittal plane, as opposed to the frontal plane, contributed to the lower heel height in participants with stage 2 AAFD. Older controls demonstrated lower heel-rise height than younger controls, indicating that clinical expectations of heel-rise performance may need to be adjusted for age.

Osteology of the coronoid process with clinical correlation to coronoid fractures in terrible triad injuries.

BACKGROUND: Terrible triad complex elbow fracture-dislocations are represented by elbow dislocations associated with fractures of the coronoid and radial head. Published literature has focused on classifying coronoid fractures by their radiographic morphology on plain x-ray images and computed tomography imaging. No study has specifically related native coronoid osteology to in situ fracture morphology. We identified 3 distinct bony regions of the coronoid, (medial, intermediate, and lateral ridges) with correlation to common fracture patterns associated with terrible triad injuries. METHODS: Coronoid osteology in 8 fresh frozen cadaveric elbows was examined, and three distinct ridges were identified and dimensions measured. RESULTS: The measurements were compared with retrospective intraoperative measurements taken of coronoid fracture fragments being stabilized during terrible triad injury repair. CONCLUSION: Classification of native coronoid process anatomy into functional ridges (medial, intermediate, lateral) may improve our understanding of coronoid fracture patterns in unstable terrible triad injuries. LEVEL OF EVIDENCE: Basic Science, Anatomic Study, Cadaver and In Vivo.