Erik Hohmann

Effects of estrogen on the mechanical behavior of the human Achilles tendon in vivo

The purpose of this study was to elucidate the effect of normal fluctuating [non-monophasic oral contraceptive pill (MOCP) users] and low, consistent (MOCP users) endogenous plasma estrogen levels on the strain behavior of the Achilles tendon in vivo. Twenty women (age 28.0 +/- 4.2 yr, height 1.67 +/- 0.07 m, mass 61.6 +/- 6.8 kg) who had been using the MOCP for at least 12 mo together with 20 matched women who were non-MOCP users (age 31.9 +/- 7.3 yr, height 1.63 +/- 0.05 m, mass 62.5 +/- 5.9 kg) participated in this study. Non-MOCP users were tested at the time of lowest (menstruation) and highest (approximately same as ovulation) estrogen, whereas MOCP users, who exhibited constant and attenuated endogenous estrogen levels, were tested at day 1 and day 14 of their cycle. At each test session, maximal isometric plantarflexion efforts were performed on a calf-raise apparatus while synchronous real-time ultrasonography of the triceps surae aponeurosis was recorded. Achilles tendon strain (%) was calculated by dividing tendon displacement during plantarflexion by resting tendon length. Repeated-measures ANOVA revealed a significant (P < 0.05) main effect of subject group with significantly lower Achilles strain (25.5%) in the MOCP users compared with the non-MOCP users. In conclusion, acute fluctuations in plasma estrogen across the menstrual cycle in non-MOCP users did not alter the strain behavior of the Achilles tendon. Conversely, long-term exposure to attenuated estrogen in MOCP users resulted in a decrease in Achilles tendon strain, which is thought to be attributed to the effects of endogenous estrogen on collagen synthesis. These findings have a number of important functional and clinical implications.

MR Imaging of the Hip and Knee Before and After Marathon Running

Background Despite its obvious benefits regarding aerobic fitness, the possible deleterious effects of long-distance running remain controversial. The repetitive loading associated with this activity could potentially predispose to the subsequent development of osteoarthritis. Lower extremity malalignment can also result in abnormal joint loading and is another possible contributing factor for premature articular cartilage degeneration. The purpose of this study is to investigate whether external impact loading in marathon runners creates internal stresses on bone and cartilage that are demonstrable on MR images. Participants were separately assessed for static lower extremity alignment, using standard radiographs. Methods Six recreational and two semi-professional runners underwent magnetic resonance (MR) imaging of the hip and knee before and after a marathon run using coronal T1-weighted and coronal STIR sequences. Results The pre-run and post-run scans failed to demonstrate marrow oedema, periosteal stress reactions, or joint effusions in seven runners. One patient who underwent a reconstruction of his anterior cruciate ligament 18 months ago demonstrated a small effusion in the reconstructed knee before and after the race. Conclusions Our results suggest that the high impact forces in long-distance running are well tolerated and subsequently do not demonstrate changes on MR images.

Does Posterior Tibial Slope Influence Knee Functionality in the Anterior Cruciate Ligament–Deficient and Anterior Cruciate Ligament–Reconstructed Knee?

PURPOSE The purpose of this study was to investigate the relation between knee functionality and posterior tibial slope in anterior cruciate ligament (ACL)-deficient and ACL-reconstructed patients. METHODS Patients with isolated ACL injuries on the surgical waiting list and patients who underwent ACL reconstruction with bone-patellar tendon-bone grafts between 18 and 24 months after surgery were recruited from the orthopaedic sports injury clinic. The study included 44 ACL-deficient patients (range 16-49) with a mean age of 26.4 years and 24 ACL-reconstructed patients with a mean age of 27.2 years (range, 25 to 49 years). Posterior tibial slope was measured on a digitalized lateral radiograph by use of the posterior tibial cortex as a reference. The Cincinnati scoring system was used to assess knee functionality. RESULTS The posterior tibial slope averaged 6.10° ± 3.57° (range, 0° to 17°) in the ACL-deficient group and 7.20° ± 4.49° (range, 0° to 17°) in the ACL-reconstructed group. An anterior tibial slope was not measured in any of the participants. The mean Cincinnati score was 62.0 ± 14.5 (range, 36 to 84) in the ACL-deficient patients and 89.3 ± 9.5 (range, 61 to 100) in the ACL-reconstructed patients. There was a moderate but nonsignificant correlation (r = 0.47) between knee functionality and slope in the ACL-deficient patients. When we divided posterior tibial slope into intervals of 0° to 4° (mean score, 58.4), 5° to 9° (mean score, 59.6), and greater than 10° (mean score, 75.4), a strong significant correlation (r = 0.91, P = .01) was observed between knee functionality and slope. There was a weak but nonsignificant correlation (r = 0.24) between knee functionality and slope in the ACL-reconstructed patients. When we divided posterior tibial slope into intervals of 0° to 4° (mean score, 78.2), 5° to 9° (mean score, 86.1), and greater than 10° (mean score, 89.4), a strong and significant correlation (r = 0.96, P = .0001) was observed between knee functionality and slope. CONCLUSIONS The results of this study suggest that ACL-deficient and ACL-reconstructed patients with higher posterior tibial slope have more functional knees. LEVEL OF EVIDENCE Level IV, therapeutic case series.

A comparison between imageless navigated and manual freehand technique acetabular cup placement in total hip arthroplasty.

The purpose of this study was to compare acetabular component positioning using an imageless system to a matched control group using conventional techniques. Thirty procedures were performed using navigation. A multislice computed tomographic scan was used to assess cup position. There was no significant difference between mean inclination (P = .11) and anteversion (P = .24) but a statistical significant difference for mean deviation from the desired position for inclination (P = .003) and anteversion (P = .007). There was a significant difference in the percentages of correctly placed cups with inclination (P = .046) and with anteversion (P = .006). Combining both anteversion and inclination, there was a significant difference (P = .01). We demonstrated a significant increase in accuracy of placement of acetabular cups within the desired position and safe zone using imageless navigation.

The influence of variable range of motion training on neuromuscular performance and control of external loads.

Clark, RA, Humphries, B, Hohmann, E, and Bryant, AL. The influence of variable range of motion training on neuromuscular performance and control of external loads. J Strength Cond Res 25(3): 704-711, 2011-Resistance training programs that emphasize high force production in different regions of the range of motion (ROM) may provide performance benefits. This study examined whether variable ROM (VROM) training, which consists of partial ROM training with countermovements performed in a different phase of the ROM for each set, results in improved functional performance. Twenty-two athletes (age 22.7 ± 2.4 years, height 1.81 ± 0.07 m, and body mass 94.6 ± 14.5 kg) with extensive resistance training backgrounds performed either a VROM or full ROM control (CON) 5-week, concentric work-matched training program. The participants were assigned to a group based on stratified randomization incorporating their strength levels and performance gains in preceding training microcycles. Testing consisted of assessing the force-ROM relationship during isokinetic and isometric bench press and ballistic bench throws, with normalized electromyography amplitude assessed during the isometric tests. Repeated-measure analyses of variance revealed that the VROM intervention significantly (p < 0.05) increased both full ROM bench throw displacement (+15.5%) and half ROM bench throw peak force (+15.7%), in addition to isokinetic peak force in the terminal ROM (13.5% increase). No significant differences were observed in the CON group or between groups for any other outcome measures. Analysis of the force-ROM relationship revealed that that the VROM intervention enhanced performance at shorter muscle lengths. These findings suggest that VROM training improves terminal and midrange performance gains, resulting in the athlete possessing an improved ability to control external loading and produce dynamic force.

Glenoid version and inclination are risk factors for anterior shoulder dislocation

HYPOTHESIS Although the contribution of the capsuloligamentous structures and dynamic muscle balance to shoulder stability has been well documented, the role of the osseous anatomy of the glenoid has not been thoroughly evaluated. This study investigated glenoid version and inclination in patients with a documented anterior shoulder dislocation and compared it with a control group. We hypothesized that patients with a prior anterior dislocation would have more anterior version and increased inferior inclination of the glenoid. MATERIALS AND METHODS Patients aged younger than 40 years who underwent arthroscopic shoulder stabilization (study group) were compared with patients (control group) who had previously undergone magnetic resonance imaging (MRI) for a different shoulder condition. Version was measured on axial images, and inclination was measured on coronal images of a T2-weighted spin-echo scan. The MRIs of 128 study group patients (mean age, 24.5 ± 8.6 years) with a confirmed traumatic anterior shoulder dislocation were compared with the MRIs of 130 control group patients (mean age, 30.9 ± 7 years). RESULTS The mean version in the study group was -1.7° ± 4.5° (retroversion); the mean inclination was 1.6° ± 5.9° (inferior). The mean version in the control group was -5.8° ± 4.6° (retroversion); the mean inclination was -4.0° ± 6.8° (superior). The between-group differences were significant for version (P = .00001) and inclination (P = .00001). CONCLUSIONS The results of this study strongly suggest that glenoid version and inclination are significantly increased in patients with established anterior shoulder instability compared with a matched control group.

Minimally invasive plating versus either open reduction and plate fixation or intramedullary nailing of humeral shaft fractures: a systematic review and meta-analysis of randomized controlled trials.

HYPOTHESIS The purpose of this study was to perform a meta-analysis comparing the clinical outcomes and complications between anterior humeral minimally invasive plate osteosynthesis (MIPO) and the 2 standard techniques, either open reduction and plating or humeral nailing. METHODS We performed a systematic review of Medline, Embase, Scopus, and Google Scholar to identify relevant randomized controlled trials in the English- and German-language literature. Eligibility criteria included randomized controlled trials comparing at least 1 surgical intervention with MIPO and reporting the primary clinical outcome using a validated functional scoring system and description of complications. Publication bias was assessed by funnel plot, and the risk of bias was established using the Cochrane Collaborations Risk of Bias Tool. Heterogeneity was assessed using χ(2) and I(2) statistics. RESULTS Eight prospective randomized studies (N = 376) met the eligibility criteria and were included in the analysis. The pooled estimate for clinical outcome showed that MIPO resulted in a significantly better outcome (standardized mean difference, 0.366; 95% confidence interval, 0.16 to 0.571; P = .0001; I(2) = 61%). The pooled estimate for all complications showed that the open reduction-internal fixation/nail group had a significantly higher complication rate (odds ratio, 0.507; 95% confidence interval, 0.285 to 0.905; P = .021; I(2) = 97%). CONCLUSION Current evidence indicates the MIPO approach has better clinical outcomes with a lower rate of complications compared with alternative surgical techniques. However, the results of this meta-analysis are limited by problems inherent in the primary studies, including poor reporting of randomization protocols, as well as possible attrition bias and reporting bias, of the primary studies. Future publications may therefore change the trend of the pooled estimate in either direction.

Anterior Pelvic Soft Tissue Thickness Influences Acetabular Cup Positioning with Imageless Navigation

The purpose of this study was to investigate acetabular component position after total hip arthroplasty correlating both version and inclination to anterior pelvic soft tissue thickness. Thirty patients with a mean age of 66.5 ± 14 (28-87) years and an average body mass index of 30.04 ± 4.6 were included. The same surgeon operated on all 30 patients, using an anterolateral approach in a supine position and an imageless navigation system. Postoperative assessment of cup inclination, cup anteversion, and soft tissue thickness was measured by an independent research associate using computed tomographic scans. Pearsons moment correlations did not reveal any significant relationships between body mass index, soft tissue thickness, final intraoperative, or postoperative cup position. Anterior soft tissue thickness had no significant effect on the accuracy of acetabular cup positioning.

Accuracy of acetabular cup positioning using imageless navigation.

BackgroundCorrect placement of the acetabular cup is a crucial step in total hip replacement to achieve a satisfactory result and remains a challenge with free-hand techniques. Imageless navigation may provide a viable alternative to free-hand technique and improve placement significantly. The purpose of this project was to assess and validate intra-operative placement values for both inclination and anteversion as displayed by an imageless navigation system to post-operative measurement of cup position using high resolution CT scans.MethodsThirty-two subjects who underwent primary hip joint arthroplasty using imageless navigation were included. The average age was 66.5 years (range 32-87). 23 non-cemented and 9 cemented acetabular cups were implanted. The desired position for the cup was 45 degrees of inversion and 15 degrees of anteversion. A pelvic CT scan using a multi-slice CT was used to assess the position of the cup radiographically.ResultsTwo subjects were excluded because of dislodgement of the tracking pin. Pearson correlation revealed a strong and significant correlation (r = 0.68; p < 0.006) for cup inclination and a moderate non-significant correlation (r = 0.53; p = 0.45) between intra-operative readings and cup placement for anteversion.ConclusionsThese findings can be explained with the possible introduction of systematic error. Even though the acquisition of anatomic landmarks is simple, they must be acquired with great precision. An error of 1 cm can result in a mean anteversion error of 6 degrees and inclination error of 2.5 degrees. Whilst computer assisted surgery results in highly accurate cup placements for inclination, anteversion of the cup cannot be determined accurately.

Lower Integrated Muscle Protein Synthesis in Masters Compared with Younger Athletes.

PURPOSE The objective of this study is to compare the integrated muscle protein synthesis (MPS) rates of masters and younger triathletes over three consecutive days of intense endurance training. Recovery of cycling performance, after muscle-damaging running, was also compared between groups. METHODS Five masters (age, 53 ± 2 yr; V˙O2max, 55.7 ± 6.9 mL·kg·min) and six younger (age, 27 ± 2 yr; V˙O2max, 62.3 ± 1.5 mL·kg·min) trained triathletes volunteered for the study. Baseline skeletal muscle and saliva were initially sampled, after which a 150-mL bolus of deuterium oxide (70%) was consumed. Participants then completed a 30-min downhill run; three 20-km cycling time trials (TT) were completed 10, 24, and 48 h after the run. Saliva was collected each morning, and skeletal muscle was again sampled 72 h after the run; both were used for MPS analysis. Diet was controlled throughout the study. RESULTS Over 3 d, masters triathletes showed a significantly lower myofibrillar fractional synthetic rate (1.49% ± 0.12%·d) compared with the younger (1.70% ± 0.09%·d) triathletes (P = 0.009, d = 1.98). There was also a trend for masters triathletes to produce a slower cycle TT (-3.0%, d = 0.46) than younger triathletes (-1.4%, d = 0.29) at 10 h postrun in comparison with the baseline performance. The between-group comparison of change was moderate (d = 0.51), suggesting slower acute recovery among masters triathletes. CONCLUSIONS The present data show lower MPS rates in well-trained masters triathletes over 3 d of training, and this likely contributes to poorer muscle protein repair and remodeling. Furthermore, acute recovery of cycle TT performance tended to be poorer in the masters triathletes.