Defining Reference Values for the Normal Adult Lisfranc Joint Using Weightbearing Computed Tomography.

The uninjured contralateral feet of consecutive patients undergoing cone-beam weightbearing computed tomography for acute Lisfranc injury between July 2017 and October 2019 were retrospectively analyzed. Of these, any cases with history or radiological evidence of trauma to the Lisfranc interval were excluded. The area of the non-weightbearing (NWBA) and weightbearing (WBA) Lisfranc joint was calculated (in mm2) using a novel technique. Area difference (AD) was calculated as WBA-NWBA. Area ratio (AR) was calculated as WBA/NWBA. A subset of cases was double-measured by 2 technologists to evaluate inter- and intraobserver variability. A total of 91 patients aged 15 to 74 years were included in the study. The measurement technique was reproducible with excellent intraobserver correlation (intraclass correlation coefficient [ICC]: 0.998, 95% confidence interval [CI]: 0.996-0.999) and high interobserver correlation (ICC: 0.964, CI: 0.939-0.979). The median NWBA was 83 (range 52-171) and median WBA was 86 (range 52-171). Median AD was 1 mm2 (range -3 to 10) and median AR was 1.01 (range 0.96-1.11). No significant difference was identified in AD or AR when adjusted for age, gender, patient-weight or weight put through the foot. Both AD and AR distributions were highly skewed toward 0 and 1, respectively. Based on 95% CI, normal reference range for AD is -1 to 7 mm2 and for AR is 0.98 to 1.09. Absolute area of the Lisfranc joint is highly variable between individuals. The Lisfranc joint is rigid with little to no physiologic widening in most subjects. The normal upper limit of widening of the Lisfranc area on weightbearing was 9%. Differences in age, sex, patient-weight or weight put through the foot were not significantly associated with the extent of joint widening.

Weightbearing Cone-Beam Computed Tomography of Acute Ankle Syndesmosis Injuries.

Syndesmotic injuries are common, but only a subset of these injuries are unstable. A noninvasive tool for identifying instability would aid in the selection of patients for surgery. Weightbearing computed tomography (CT) data have been reported for healthy patients, but there are limited data on unstable syndesmoses. We evaluated the syndesmotic area of arthroscopically proven unstable ankles after acute injury. This is a prospective comparative study of consecutive patients recruited to a weightbearing CT database. Thirty-nine patients were included for analysis with arthroscopically proven unstable syndesmoses and an uninjured contralateral ankle. The syndesmosis area was measured for both ankles, in non-weightbearing and weightbearing positions, and compared. Syndesmosis area of the unstable ankle was significantly greater than the uninjured ankle of the same patient, by a mean of 22.9 ± 10.5 mm2. This was a significantly greater difference than that observed with non-weightbearing CT (9.8 ± 10.2 mm2, p < .001). Dynamic change in area, from non-weightbearing to weightbearing, of the unstable ankle (13.7% [16.6 ± 9.9 mm2]) was significantly greater than that of the uninjured ankle (3.1% [3.4 ± 6.7 mm2], p < .001). The intraobserver and interobserver correlations were good with intraclass correlation coefficients of 0.983 and 0.970, respectively. Weightbearing CT demonstrated significantly greater diastasis in unstable ankles than did conventional non-weightbearing CT. Syndesmosis area measurement was reliable and reproducible. Dynamic change in area and weightbearing comparison with the contralateral uninjured ankle are 2 parameters that may prove useful in the future for predicting syndesmotic instability.

Comparison of 3 Different Perioperative Care Models for Patients With Hip Fractures Within 1 Health Service.

INTRODUCTION: Orthogeriatric care models have been introduced within many health-care facilities to improve outcomes for hip fracture patients. This study aims to evaluate differences in care between 3 models, an orthopedic model, a geriatric model, and a comanaged model. MATERIALS AND METHODS: A retrospective analysis was conducted for hip fracture patients treated at Western Health between November 2012 and March 2014. All patients aged 65 years or older were included in the analysis. RESULTS: There were 183 patients in the orthopedic model, 137 in the geriatric model, and 126 in the comanaged model. Demographics and clinical characteristics were similar across the 3 models. Length of stay, mortality, and discharge destination were also consistent across the 3 groups. However, groups involving geriatricians were more likely to receive preoperative medical assessments, have greater recognition of postoperative medical problems, and have implementation of long-term osteoporosis management. CONCLUSION: The involvement of geriatricians in perioperative care models resulted in more comprehensive medical care without impacting length of stay, mortality, or discharge destination.

Muscle and joint-contact loading at the glenohumeral joint after reverse total shoulder arthroplasty.

The purposes of this study were to determine the contributions of each shoulder muscle to glenohumeral joint force during abduction and flexion in both the anatomical and post-operative shoulder and to identify factors that may contribute to the incidence of glenoid component loosening/failure and joint instability in the shoulder after reverse shoulder arthroplasty (RSA). Eight cadaveric upper extremities were mounted onto a testing apparatus. Muscle lines of action were measured, and muscle forces and muscle contributions to glenohumeral joint forces were determined during abduction and flexion of the pre-operative anatomical shoulder and of the shoulder after arthroplasty. Muscle forces in the middle deltoid during abduction and those in the middle and anterior deltoid during flexion were significantly lower in the reverse shoulder than the pre-operative shoulder (p < 0.017). The resultant glenohumeral joint force in the reverse shoulder was significantly lower than that in the pre-operative shoulder; however, the superior shear force acting at the glenohumeral joint was significantly higher (p < 0.001). Reverse total shoulder arthroplasty reduces muscle effort in performing lifting and pushing tasks; however, reduced joint compressive force has the potential to compromise joint stability, while an increased superior joint shear force may contribute to component loosening/failure. Because greater superior shear force is generated in flexion than in abduction, care should be taken to avoid excessive shoulder loading in this plane of elevation.

Moment arms of the shoulder musculature after reverse total shoulder arthroplasty.

BACKGROUND: Reverse total shoulder arthroplasty is known to increase the moment arm of the middle subregion of the deltoid during shoulder abduction; however, at present, comprehensive data regarding the shoulder muscle moment arm through the full range of abduction and flexion are not available. The purpose of this study was twofold: (1) to measure the instantaneous moment arms of thirteen subregions of major muscles spanning the glenohumeral joint during abduction and flexion of the shoulder after reverse total shoulder arthroplasty and (2) to compare these data with the muscle moment arms previously measured preoperatively in the anatomical shoulders. METHODS: Reverse total shoulder arthroplasty was performed on eight entire cadaveric upper extremities. The specimens were mounted onto a dynamic testing apparatus, and the instantaneous abductor/adductor and flexor/extensor moment arms of subregions of the deltoid, latissimus dorsi, pectoralis major, teres major, and subscapularis muscles (a total of thirteen subregions) were measured with use of the tendon excursion method. These muscle moment arms were compared with those measured preoperatively in the anatomical shoulders. RESULTS: Reverse total shoulder arthroplasty resulted in significant increases in the abductor moment arms of the anterior subregion of the deltoid (mean increase = 10.4 mm; 95% confidence interval = 7.5 to 13.3 mm) and the middle subregion of the deltoid (mean increase = 15.5 mm; 95% confidence interval = 10.8 to 20.3 mm) as well as recruitment of the posterior subregion of the deltoid as an abductor. The superior subregion of the pectoralis major (the clavicular fibers) and anterior subregion of the deltoid were the most effective flexors and had a substantial potential to initiate flexion. The adductor and extensor moment arms of the teres major, latissimus dorsi subregions, and inferior and middle subregions of the pectoralis major increased substantially after the arthroplasty. The subscapularis subregions behaved as extensors, abductors, and adductors after the arthroplasty; this was in contrast to their roles in the anatomical shoulder, in which they were mainly flexors and adductors. CONCLUSIONS: Reverse total shoulder arthroplasty increases the moment arms of the major abductors, flexors, adductors, and extensors of the glenohumeral joint, thereby reducing muscle effort during common tasks such as lifting and pushing.