Spring-mass behavioural adaptations to acute changes in prosthetic blade stiffness during submaximal running in unilateral transtibial prosthesis users.

BACKGROUND: Individuals with lower-limb amputation can use running specific prostheses (RSP) that store and then return elastic energy during stance. However, it is unclear whether varying the stiffness category of the same RSP affects spring-mass behaviour during self-selected, submaximal speed running in individuals with unilateral transtibial amputation. RESEARCH QUESTION: The current study investigates how varying RSP stiffness affects limb stiffness, running performance, and associated joint kinetics in individuals with a unilateral transtibial amputation. METHODS: Kinematic and ground reaction force data were collected from eight males with unilateral transtibial amputation who ran at self-selected submaximal speeds along a 15 m runway in three RSP stiffness conditions; recommended habitual stiffness (HAB) and, following 10-minutes of familiarisation, stiffness categories above (+1) and below (-1) the HAB. Stance-phase centre of mass velocity, contact time, limb stiffness' and joint/RSP work were computed for each limb across RSP stiffness conditions. RESULTS: With increased RSP stiffness, prosthetic limb stiffness increased, whilst intact limb stiffness decreased slightly (p<0.03). Centre of mass forward velocity during stance-phase (p<0.02) and contact time (p<0.04) were higher in the intact limb and lower in the prosthetic limb but were unaffected by RSP stiffness. Intact limb hip joint positive work increased for both the +1 and -1 conditions but remained unchanged across conditions in the prosthetic limb (p<0.02). SIGNIFICANCE: In response to changes in RSP stiffness, there were acute increased mechanical demands on the intact limb, reflecting a reliance on the intact limb during running. However, overall running speed was unaffected, suggesting participants acutely adapted to an RSP of a non-prescribed stiffness.

Pelvic organ motion and dosimetric implications during horizontal patient rotation for prostate radiation therapy.

PURPOSE: Gantry-free radiation therapy systems utilizing patient rotation would be simpler and more cost effective than the conventional gantry-based systems. Such a system could enable the expansion of radiation therapy to meet global demand and reduce capital costs. Recent advances in adaptive radiation therapy could potentially be applied to correct for gravitational deformation during horizontal patient rotation. This study aims to quantify the pelvic organ motion and the dosimetric implications of horizontal rotation for prostate intensity-modulated radiation therapy (IMRT) treatments. METHODS: Eight human participants who previously received prostate radiation therapy were imaged in a clinical magnetic resonance imaging (MRI) scanner using a bespoke patient rotation system (PRS). The patients were imaged every 45 degrees during a full roll rotation (0-360 degrees). Whole pelvic bone, prostate, rectum, and bladder motion were compared to the supine position using dice similarity coefficient (DSC) and mean absolute surface distance (MASD). Prostate centroid motion was compared in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) direction prior to and following pelvic bone-guided rigid registration. Seven-field prostate IMRT treatment plans were generated for each patient rotation angles under three adaption scenarios: No plan adaption, rigid planning target volume (PTV)-guided alignment to the prostate, and plan re-optimization. Prostate, rectum, and bladder doses were compared for each adaption scenario. RESULTS: Pelvic bone motion within the PRS of up to 53 mm relative to the supine position was observed for some participants. Internal organ motion was greatest at the 180-degree PRS couch angle (prone), with prostate centroid motion range < 2 mm LR, 0 mm to 14 mm SI, and -11 mm to 4 mm AP. Rotation with no adaption of the treatment plan resulted in an underdose to the PTV -- in some instances up to 75% (D95%: 78 ± 0.3 Gy at supine to 20 ± 15.0 Gy at the 225-degree PRS couch angle). Bladder dose was reduced during the rotation by up to 98% (V60 Gy: 15.0 ± 9.4% supine to 0.3 ± 0.5% at the 225-degree PRS couch angle). In some instances, the rectum dose increased during rotation (V60Gy: 20.0 ± 4.5% supine to 25.0 ± 15.0% at the 135-degree PRS couch angle). Rigid PTV-guided alignment resulted in PTV coverage which, though statistically lower (P < 0.05 for all D95% values), was within 1 Gy of the supine plans. Plan re-optimization resulted in a statistically equivalent PTV coverage compared to the supine plans (P > 0.05 for all D95% metrics and all within ±0.4 Gy). For both rigid PTV-guided alignment and plan re-optimization, rectum dose volume metrics were reduced compared to the supine position between the 90- and 225-degree PRS couch angles (P < 0.05). Bladder dose volume metrics were not impacted by rotation. CONCLUSION: Pelvic bone and internal organ motion are present during patient rotation. Rigid PTV-guided alignment to the prostate will be a requirement if prostate IMRT is to be safely delivered using patient rotation. Plan re-optimization for each PRS couch angle to account for anatomical deformations further improves the PTV coverage.

Anatomical deformation due to horizontal rotation: towards gantry-free radiation therapy.

Gantry-free radiation therapy systems may be simpler and more cost effective, particularly for MRI-guided photon or hadron therapy. This study aims to understand and quantify anatomical deformations caused by horizontal rotation with scan sequences sufficiently short to facilitate integration into an MRI-guided workflow. Rigid and non-rigid pelvic deformations due to horizontal rotation were quantified for a cohort of 8 healthy volunteers using a bespoke patient rotation system and a clinical MRI scanner. For each volunteer a reference scan was acquired at 0° followed by sequential faster scans in 45° increments through to 360°. All fast scans were registered to the 0° image via a three-step process: first, images were aligned using MR visible couch markers. Second, the scans were pre-processed then rigidly registered to the 0° image. Third, the rigidly registered scans were non-rigidly registered to the 0° image to assess soft tissue deformation. The residual differences after rigid and non-rigid registration were determined from the transformation matrix and the deformation vector field, respectively. The rigid registration yielded mean rotations of ⩽2.5° in all cases. The average 3D translational magnitudes range was 5.8 ± 2.9 mm-30.0 ± 11.0 mm. Translations were most significant in the left-right (LR) direction. Smaller translations were observed in the anterior-posterior (AP) and superior-inferior (SI) directions. The maximum deformation magnitudes range was: 10.0 ± 0.9 mm-28.0 ± 2.8 mm and average deformation magnitudes range: 2.3 ± 0.6 mm-7.5 ± 1.0 mm. Average non-rigid deformation magnitude was correlated with BMI (correlation coefficient 0.84, p  = 0.01). Rigid pelvic deformations were most significant in the LR direction but could be accounted for with on-line adjustments. Non-rigid deformations can be significant and will need to be accounted for in order to facilitate the delivery of gantry-free therapy with an automated patient rotation system.

The mechanics of landing when stepping down in unilateral lower-limb amputees.

BACKGROUND: The ability to successfully negotiate stairs and steps is an important factor for functional independence. While work has been undertaken to understand the biomechanics of gait in lower-limb amputees, little is known about how amputees negotiate stairs and steps. This study aimed to determine the mechanics of landing in unilateral lower-limb amputees when stepping down to a new level. A secondary aim was to assess the effects of using a shank-mounted shock-absorbing device (Tele-Torsion Pylon) on the mechanics of landing. METHODS: Ten unilateral amputees (five transfemoral and five transtibial) and eight able-bodied controls performed single steps down to a new level (73 and 219 mm). Trials were repeated in amputees with the Tele-Torsion Pylon active and inactive. The mechanics of landing were evaluated by analysing peak limb longitudinal force, maximal limb shortening, lower extremity stiffness, and knee joint angular displacement during the initial contact period, and limb and ankle angle at the instant of ground-contact. Data were collected using a Vicon 3D motion analysis system and two force platforms. FINDINGS: Amputees landed on a straightened and near vertical limb. This limb position was maintained in transfemoral amputees, whereas in transtibial amputees knee flexion occurred. As a result lower extremity stiffness was significantly greater in transfemoral amputees compared to transtibial amputees and able-bodied controls (P<0.001). The Tele-Torsion Pylon had little effect on the mechanics of landing in transtibial amputees, but brought about a reduction in lower extremity stiffness in transfemoral amputees (P<0.05). INTERPRETATION: Amputees used a stepping strategy that ensured the direction of the ground reaction force vector was kept anterior of the knee joint centre. Using a Tele-Torsion Pylon may improve the mechanics of landing during downward stepping in transfemoral amputees.

The gait initiation process in unilateral lower-limb amputees when stepping up and stepping down to a new level.

BACKGROUND: Unilateral lower-limb amputees lead with their intact limb when stepping up and with their prosthesis when stepping down; the gait initiation process for the different stepping directions has not previously been investigated. METHODS: Ten unilateral amputees (5 transfemoral and 5 transtibial) and 8 able-bodied controls performed single steps up and single steps down to a new level (73 and 219 mm). Duration, a-p and m-l centre of mass and centre of pressure peak displacements and centre of mass peak velocity of the anticipatory postural adjustment and step execution phase were evaluated for each stepping direction by analysing data collected using a Vicon 3D motion analysis system. FINDINGS: There were significant differences (in the phase duration, peak a-p and m-l centre of pressure displacement and peak a-p and m-l centre of mass velocity at heel-off and at foot-contact) between both amputee sub-groups and controls (P<0.05), but not between amputee sub-groups. These group differences were mainly a result of amputees adopting a different gait initiation strategy for each stepping direction. INTERPRETATION: Findings indicate the gait initiation process utilised by lower-limb amputees was dependent on the direction of stepping and more particularly by which limb the amputee led with; this suggests that the balance and postural control of gait initiation is not governed by a fixed motor program, and thus that becoming an amputee will require time and training to develop alternative neuromuscular control and coordination strategies. These findings should be considered when developing training/rehabilitation programs.

Chronic low back pain in traumatic lower limb amputees.

OBJECTIVE: To ascertain the prevalence of back pain amongst traumatic lower limb amputees attending a regional rehabilitation centre and to determine the possible causes of back pain. DESIGN: All traumatic lower limb amputees given a semi-structured questionnaire to complete and a comparative subgroup of amputees with back pain and without back pain underwent physical examination, gait analysis, magnetic resonance scanning (MRI) and gait/standing stability analysis. SETTING: A subregional amputee rehabilitation centre. RESULTS: Transfemoral amputees were more likely to suffer from back pain (81 %) than transtibial amputees (62%) (p<0.05) and of those suffering from severe back pain, 89% and 81% also suffered from severe pain in the phantom limb and severe stump pain respectively. In two comparative subgroups of amputees there was no significant difference between back pain and pain-free groups except those with pain were more likely to have a body mass index (BMI) ratio above 50% of the recommended ratio. No difference in degeneration or disc disease between the groups on MR scans was found. Impact ground reaction forces during walking, irrespective of limb, were significantly greater (p < 0.05) in the pain-free group than in the pain group, as was walking speed. Gait asymmetry measures were similar in both groups. Centre of pressure displacement measures during standing were greater in the pain group than in the pain-free group. CONCLUSIONS: Low back pain in amputees is a significant problem equal to that of pain in the phantom limb and a biomechanical (myofascial) rather than a degenerative aetiology is suggested.

Surgical treatment of cervical node metastases from squamous carcinoma of the upper aerodigestive tract: evaluation of the evidence for modifications of neck dissection.

BACKGROUND: This review article examines the role of the different types of neck dissection in the treatment of squamous carcinoma metastases to the cervical nodes. METHODS: A critical evaluation of the literature on the pathologic basis, oncologic effectiveness, and functional outcome of neck dissection. RESULTS: Pathologic data show preferential metastasis to different lymph node levels, in N0- and N+-staged disease, depending on the primary tumor site. Comparative studies on control of regional metastases suggest that modified radical is no less effective than radical neck dissection, but there is insufficient data to draw firm conclusions on the role of selective neck dissection. Selective and modified radical dissections result in less shoulder disability than radical neck dissection. CONCLUSIONS: Modified radical neck dissection is supported by pathologic and clinical evidence in N1- and 2-staged disease. There may be a role for selective dissection, but there is a need for more information on oncologic outcome. Prospective multicenter systematic data collection on the outcome of neck dissection is a pragmatic alternative to a trial.

General considerations on distant metastases from head and neck cancer.

Mortality in head and neck cancer is due to locoregional disease, distant metastases or intercurrent disease. As treatment of the primary tumor and cervical metastases has improved, the proportion of deaths from co-morbidity and from distant metastases has increased. Distant metastases almost invariably herald a poor prognosis in head and neck cancer with an average survival of 4.3-7.3 months and treatment is usually palliative. Reliable detection is important to prevent inappropriate treatment. The risk is related to the site, stage and histology of the primary tumor and the presence of cervical metastases. Early detection and treatment of cervical metastases may prevent distant metastases. Accurate staging of tumors helps to identify high-risk tumors that should be specifically investigated for distant metastases.

Screening tests to evaluate distant metastases in head and neck cancer.

Investigation for distant metastases is part of the staging process of a primary tumor or recurrent disease before treatment. The lung is the most frequent site followed by bone and liver. Advanced stage and cervical metastases are the most important predictors of metastases. Almost all distant metastases are associated with lung metastases. Computed tomography scan of the chest is the single most effective investigation. The value of routine screening tests is questionable and merits further investigation.

The treatment of distant metastases in head and neck cancer--present and future.

At the present time the occurrence of distant metastases in patients with head and neck squamous cell carcinoma means that lifespan is measured in months. In most instances treatment is purely palliative. Isolated lung metastasis can be successfully removed with long-term disease control in selected patients. Radiotherapy can be useful for palliation of bone metastases and occasionally lung or brain metastases. Chemotherapy does not have a major impact at the present time except for the treatment of metastases from nasopharyngeal cancer. Palliative symptomatic care, along with appropriate pain control, is essential since pain management is very important in these patients. A significant change in the survival of patients with head and neck cancer is only likely to occur by the development of new approaches to treatment. Blocking tumor angiogenesis and treatment based on genetic abnormalities or cell surface receptors offer the two strategies that are most likely to be successful.

Muscle power patterns in the mid-acceleration phase of sprinting.

To assess the role of the lower limb joints in generating velocity in the mid-acceleration phase of sprinting, muscle power patterns of the hip, knee and ankle were determined. Six male sprinters with a mean 100 m time of 10.75 s performed repeated maximal sprints along a 35 m indoor track. A complete stride across a force platform, positioned at approximately 14 m into the sprint, was video-recorded for analysis. Smoothed coordinate data were obtained from manual digitization of (50 Hz) video images and were then interpolated to match the sampling rate of the recorded ground reaction force (1000 Hz). The moment at each joint was then calculated using inverse dynamics and multiplied by the angular velocity to determine the muscle power. The results showed a proximal-to-distal timing in the generation of peak extensor power during stance at the hip, the knee and then the ankle, with the plantar flexors producing the greatest peak power. Apart from a moderate power generation peak towards toe-off, knee power was negligible despite a large extensor moment throughout stance. The role of the knee thus appears to be one of maintaining the centre of mass height and enabling the power generated at the hip to be transferred to the ankle.

Cervical node metastases in laryngeal and hypopharyngeal cancer: a prospective analysis of prevalence and distribution.

BACKGROUND: We have prospectively analyzed the prevalence and distribution of histologic cervical node metastases in laryngeal and hypopharyngeal squamous carcinoma to determine the most appropriate form of neck dissection. METHODS: We have examined specimens from 100 consecutive patients in whom neck dissection was part of the primary treatment of laryngeal and hypopharyngeal carcinoma. Fifty eight patients were treated by unilateral or bilateral selective dissection of levels I to IV +/- VI for N0 disease and 42 by comprehensive dissection for N+ disease. Assessment was by separation of the specimens into node levels at the time of surgery and embedding all the resected material for histologic analysis. RESULTS: Nodal metastases were found in 36% of ipsilateral and 27% of contralateral dissections in the N0 cases. The corresponding prevalences in N+ cases were 90% and 37%, respectively. All metastases in N0 and N1 disease were confined to levels II, III, IV, and VI. Metastases to levels I and V were infrequent even in N+ disease. CONCLUSIONS: Our results support the use of elective dissection of node levels II to IV for N0 laryngeal and hypopharyngeal carcinoma. We suggest the inclusion of level VI nodes for tumors invading the subglottis, pyriform fossa apex, and postcricoid region. The prevalence of bilateral metastases is great enough in midline or bilateral tumors to justify bilateral selective dissection. It is possible that selective neck dissection is also adequate for small palpable metastases, but greater numbers are required to confirm this.