Untangling biomechanical differences in perturbation-induced stepping strategies for lateral balance stability in older individuals.

When recovering balance from a lateral perturbation, younger adults tend to stabilize balance with a single lateral sidestep while older adults often take multistep responses. Using multiple steps to recover balance is consistently associated with increased fall risk, altered body center of mass (CoM) control and instability. The aim of this study was to compare the spatio-temporal stepping characteristics and the margin of stability (MoS) of single lateral sidesteps (LSS1) with the first and second steps of a two-step protective step sequence. Two-step sequences begin with either a cross-over step to the front or back, or a medial step followed by a lateral sidestep. Seventy-one older adults received random lateral waist-pull perturbations to either side. We hypothesized that LSS1 would be more stable (larger MoS) than either step in a two-step sequence. With some exceptions, utilizing a two-step sequence was associated with a reduced CoM velocity and distance between the base of support and CoM and decreased stability in the frontal plane following limb loading of the first and second step. There were no differences in the time available to arrest the extrapolated CoM at the end of a single lateral sidestep or the final step of a two-step sequence. Two-step sequences involving a cross-over step include more complex stepping trajectories and also challeng stability in the sagittal plane requiring a multidimensional balance correction. These results indicate important step type differences in center of mass control in recovering balance with a single lateral sidestep as opposed to a two-step sequence among older adults.

Extending the center of pressure to incorporate handhold forces: Derivation and sample application.

Measures describing movement of the center of pressure (CoP) are frequently used to characterize postural control. Estimates of CoP often focus on forces that individuals exert in a single plane through the feet (standing on force plates). However, balance may also be supported by forces other than those developed at the feet, especially when walkers, handrails, and other aids are used. In these cases, it is common to neglect the contributions of handheld supports. Here, we derive and apply equations for an extended CoP that incorporates handhold forces. We then examine the influence of CoP definition (i.e., including or ignoring handhold forces) on common metrics (path length; RMS and maximum excursion; average and maximum velocity) for 12 younger adults with a handrail located lateral to the participants' dominant hand. Participants attempted balance recovery in response to a range of small, medium and large forward and backward platform translations. Significant interactions between perturbation magnitude and CoP definition were found for most metrics. Notably, the interaction of CoP definition and perturbation magnitude significantly affected path length (p-values < 0.001). Post-hoc analyses revealed larger CoP path length when handrail forces were incorporated in CoP estimates compared to ignoring handrail forces at medium (backward: 59.9 vs. 19.0% height; forward: 70.5 vs 22.4% height) and large perturbation magnitudes (backward: 69.9 vs 22.4% height; forward: 103.5 vs 24.6% height). Incorporation of hand forces in CoP calculations can present a different view of postural balance control than relying on a feet-only CoP. This measure could be useful in assessing balance control tasks that involve the use of handrails or hand-held mobility devices.

Perturbation-evoked lateral steps in older adults: Why take two steps when one will do?

BACKGROUND: Hip fractures in older adults often result from a fall in the lateral direction. While younger adults tend to recover balance from a lateral perturbation with a single lateral sidestep, older adults are prone to multistep responses which are associated with an increased fall risk. This study compared the stepping characteristics and stability of single and multistep responses to lateral perturbation in healthy older adults. METHODS: Eighty-four older adults received lateral waist-pull perturbations to either side. Spatio-temporal stepping characteristics and balance stability were quantified. FINDINGS: Fewer steps were taken to recover balance when the first step was a lateral sidestep. The stability margin of single lateral sidesteps was greater than medial sidesteps and cross-over steps to the back but not significantly different from single cross-over steps to the front at step termination. Single step responses were more stable than multistep responses at step termination and at step initiation for lateral sidesteps and cross-over steps to the front. The decreased stability of multistep responses was attributed to an increased center of mass velocity and a smaller distance between the center of mass and base-of-support at step termination. INTERPRETATION: Although lateral sidesteps result in fewer steps than cross-over steps to the front, the stability margin was not significantly different at step termination. These results suggest difficulty terminating center of mass motion and/or inefficient center of mass control differentiates single and multistep responses. Future studies should investigate perturbation training and/or hip abductor muscle conditioning as a means of improving compensatory stepping reactions.

Functional outcome after fracture of both bones of the forearm.

Our aim was to correlate the health status with objective and radiological outcomes in patients treated by open reduction and internal fixation for fractures of both bones of the forearm. We assessed 23 patients (24 fractures) subjectively, objectively and radiologically at a mean of 34 months (11 to 72). Subjective assessment used the disability of the arm, shoulder and hand (DASH) and musculoskeletal functional attachment (MFA) questionnaires. The range of movement of the forearm and wrist, grip and pinch strength were measured objectively and standardised radiographs were evaluated. In general, patients reported good overall function based on the DASH (mean 12; range 0 to 42) and MFA (mean 19; range 0 to 51) scores. However, pronation and grip and pinch strength were significantly decreased (p < 0.005). These deficiencies correlated with poorer subjective outcomes. Operative stabilisation of fractures of the radius and ulna led to a reliably acceptable functional outcome. However, despite these generally satisfactory results, the outcome scores worsened with reduction in the range of movement of the forearm and wrist.

Fractures of the proximal third of the tibial shaft treated with intramedullary nails and blocking screws.

OBJECTIVES: To describe the technique and results of using blocking screws and intramedullary nails to treat patients with fractures of the proximal third of the tibial shaft. DESIGN: Prospective. SETTING: Level I trauma centers. PATIENTS: Twelve consecutive patients treated with intramedullary nailing and blocking screws for fractures of the proximal third of the tibial shaft. INTERVENTION: Patients were treated with intramedullary nails and blocking screws. MAIN OUTCOME MEASURE: The alignment of fractures was determined using standard anteroposterior and lateral radiographs after surgery and at each follow-up examination. One patient was lost to follow-up. All other patients were followed at regular intervals until union or establishment of a nonunion. Changes in alignment and complications were noted. RESULTS: Postoperatively, all patients had less than 5 degrees of angular deformity in the planes in which blocking screws were used to control alignment. One patient had postoperative malalignment (6 degrees of valgus), but a lateral blocking screw to control valgus deformity was not used in this patient. One patient was lost to follow-up. Eleven patients were followed up to union (n = 10) or establishment of a nonunion (n = 1). Ten of eleven patients maintained their postoperative fracture alignment at their last follow-up examination (average follow-up of thirty-three weeks). One patient progressed from 6 degrees of valgus immediately after surgery to 10 degrees of valgus at union. This patient did not have a blocking screw to control valgus angulation. CONCLUSIONS: Blocking screws are effective to help obtain and maintain alignment of fractures of the proximal third of the tibial shaft treated with intramedullary nails.

Pelvic fracture and associated urologic injuries.

Successful management of patients with major pelvic injuries requires a team approach including orthopedic, urologic, and trauma surgeons. Each unstable pelvic disruption must be treated aggressively to minimize complications and maximize long-term functional outcome. Commonly associated urologic injuries include injuries of the urethra, corpora cavernosa (penis), bladder, and bladder neck. Bladder injuries are usually extraperitoneal and result from shearing forces or direct laceration by a bone spicule. Posterior urethral injuries occur more commonly with vertically applied forces, which typically create Malgaigne-type fractures. Common complications of urethral disruption are urethral stricture, incontinence, and impotence. Acute urethral injury management is controversial, although it appears that early primary realignment has promise for minimizing the complications. Impotence after pelvic fracture is predominantly vascular in origin, not neurologic as once thought.

Intraneural sciatic nerve pressures relative to the position of the hip and knee: a human cadaveric study.

OBJECTIVES: To determine the effects of ipsilateral hip and knee position on intraneural sciatic nerve pressures. DESIGN: Intraneural sciatic nerve pressures measured in intact, fresh cadaveric specimens relative to ipsilateral hip and knee positions. LOCATION: Medical school anatomy laboratory. SUBJECTS: Randomly acquired adult cadavers. INTERVENTION: Pressure transducer placed within the sciatic nerve distal to the femoral attachment of the gluteus maximus. Intraneural pressures measured with the hip placed in 0, 45, and 90 degrees of flexion while the knee was positioned in 90, 45, and 0 degrees of flexion. MAIN OUTCOME MEASUREMENTS: Tissue fluid pressures within the sciatic nerve relative to the position of the ipsilateral hip and knee. Tissue fluid pressure within the sciatic nerve exceeded previously defined critical thresholds for alteration of neural microcirculation and function. Although increased intraneural pressures were realized as the hip was positioned in greater flexion and the knee was extended, clinically relevant pressures were realized only when the hip was flexed to 90 degrees and the knee was fully extended. Pressures with the limbs in these positions were fifty-five millimeters of mercury (range 38 to 74 millimeters of mercury). RESULTS: With the hip held flexed to 90 degrees, statistically significantly increased intraneural pressures were measured as the knee was extended from 90 to 45 degrees of flexion (p = 0.048) and again from 45 to 0 degrees of flexion (p < or = 0.01). With the knee positioned in 45 degrees of flexion, statistically significantly increased intraneural pressures were measured as the hip was flexed from 45 to 90 degrees (p < or = 0.0062). When the knee was held fully extended, statistically significantly increased intraneural pressures were measured as the hip was flexed from 0 to 45 degrees of flexion (p = 0.0006) and again when the hip was brought from 45 to 90 degrees of flexion (p < or = 0.01). CONCLUSIONS: Intraneural sciatic nerve pressures are influenced by the position of the ipsilateral hip and knee. The magnitude of the pressure elevation appears to be related to the excursion of the nerve as the linear distance between the greater sciatic notch and the distal aspect of the leg increases. Intraneural tissue fluid pressures measured within a localized section of the sciatic nerve appeared to exceed published critical thresholds for alterations of blood flow and neural function only when the hip was flexed to 90 degrees and the knee was fully extended.

Effect of impact load on articular cartilage: cell metabolism and viability, and matrix water content.

Significant evidence exists that trauma to a joint produced by a single impact load below that which causes subchondral bone fracture can result in permanent damage to the cartilage matrix, including surface fissures, loss of proteoglycan, and cell death. Limited information exists, however, on the effect of a varying impact stress on chondrocyte biophysiology and matrix integrity. Based on our previous work, we hypothesized that a stress-dependent response exists for both the chondrocyte's metabolic activity and viability and the matrix's hydration. This hypothesis was tested by impacting bovine cartilage explants with nominal stresses ranging from 0.5 to 65 MPa and measuring proteoglycan biosynthesis, cell viability, and water content immediately after impaction and 24 hours later. We found that proteoglycan biosynthesis decreased and water content increased with increasing impact stress. However, there appeared to be a critical threshold stress (15-20 MPa) that caused cell death and apparent rupture of the collagen fiber matrix at the time of impaction. We concluded that the cell death and collagen rupture are responsible for the observed alterations in the tissue's metabolism and water content, respectively, although the exact mechanism causing this damage could not be determined.

Vascularity of the lateral calcaneal flap: a cadaveric injection study.

OBJECTIVE: To describe the arterial blood supply of the subcutaneous tissues of the lateral hindfoot and define the relationships between these arteries and the lateral extensile incision used for open reduction and internal fixation of calcaneal fractures. DESIGN: Human cadaveric lower extremity specimens, doubly injected with India ink and latex, were used to demonstrate the location of the arteries of the subcutaneous tissues of the lateral hindfoot. SETTING: Anatomy laboratory. PATIENTS/PARTICIPANTS: Twenty-four randomly obtained, cadaveric elderly lower extremity specimens. INTERVENTION: India ink and then latex were injected into the superficial femoral artery at the level of the inguinal crease after cleansing of the arterial system. Transtibial amputation specimens were manually debrided of the skin and chemically debrided of subcutaneous tissues with sodium hypochlorite to demonstrate the arterial supply to the soft tissues of the lateral hindfoot. MEAN OUTCOME MEASUREMENTS: The location of the three major arteries was determined relative to the lateral malleolus. The proximity of these vessels to the typical extensile lateral incision was determined radiographically with vascular clips applied along each artery and skin staples placed along the path of the typical skin incision. RESULTS: Three arteries, the lateral calcaneal artery, the lateral malleolar artery, and the lateral tarsal artery, were consistently found along the lateral aspect of the hindfoot. The lateral calcaneal artery appeared to be responsible for the majority of the blood supply to the corner of the flap and, because of its proximity to the vertical portion of the typical incision, it appeared most likely to be injured from inaccurate placement of the incision. CONCLUSIONS: The development of wound complications following open reduction and internal fixation of the calcaneus is multifactorial. Disruption of the blood supply to the surgically created flap may play a larger role in the development of wound complications than previously thought. An understanding of the local vascular anatomy may decrease the rate of wound complications during the operative treatment of intraarticular calcaneal fractures.

Displaced intra-articular fractures of the distal aspect of the radius. Long-term results in young adults after open reduction and internal fixation.

The purpose of this retrospective study was to determine the long-term functional and radiographic outcomes in a series of young adults (less than forty-five years old) in whom an acute displaced intra-articular fracture of the distal aspect of the radius had been treated with operative reduction and stabilization. Twenty-six fractures in twenty-six patients met the initial inclusion criteria for the study. Twenty-one patients returned for a physical examination, imaging (plain radiographs and computerized tomography scans), and completion of a validated musculoskeletal function assessment questionnaire at a minimum of 5.5 years. The physical examinations were performed by the same observer, who was not involved in the initial care of the patients. The plain radiographs and computerized tomography scans were assessed in a blinded fashion by two independent observers who measured the radiographic parameters with standardized methods. At an average of 7.1 years, osteoarthrosis of the radiocarpal joint was evident on the plain radiographs and computerized tomography scans of sixteen (76 per cent) of the twenty-one wrists. A strong association was found between the development of osteoarthrosis of the radiocarpal joint and residual displacement of articular fragments at the time of osseous union (p < 0.01). However, the functional status at the time of the most recent follow-up, as determined by physical examination and on the basis of the responses on the questionnaire, did not correlate with the magnitude of the residual step and gap displacement at the time of fracture-healing. All patients had a good or excellent functional outcome irrespective of radiographic evidence of osteoarthrosis of the radiocarpal or the distal radio-ulnar joint or non-union of the ulnar styloid process. It appears prudent therefore to base the indications for salvage operative procedures on the presence of severe symptoms or a loss of function rather than on radiographic evidence of osteoarthrosis of the radiocarpal joint.

Effect of impact load on articular cartilage: development of an intra-articular fracture model.

OBJECTIVES: To investigate the biological and mechanical effects of a single-impact load on articular cartilage. DESIGN: An in vitro laboratory study was performed using mature bovine cartilage and bone, and isolated cartilage explants. Each specimen was impacted with a single load applied with a specially designed impactor and materials test machine. Chondrocyte metabolic activity and cartilage structural integrity was investigated using force displacement curves, radionuclide labeling, histology, and changes in water content. SETTING: Laboratory for Soft Tissue Research, New York, New York, U.S.A. SPECIMENS: Viable mature bovine cartilage and cartilage and bone explants. MAIN OUTCOME MEASUREMENTS: Mechanical failure, proteoglycan synthesis, water content, histology, radiography, and scanning electron microscopy changes occurring during the twenty-four-hour period immediately following impact. RESULTS: Force/displacement curves for the cartilage and bone explants demonstrated two failure-stress peaks, the first at fifty megapascals, representing cartilage failure, and a second peak at seventy-five megapascals, representing bone failure. Fine grain radiographs, histology, and scanning electron microscopy all confirmed the destruction of the cartilage in the area of direct impact (zone I) and subchondral bone failure and the detachment of the cartilage within the lesser impacted area (zone II). Proteoglycan synthesis was reduced significantly (p < 0.05) in the areas of direct impact (zone I) compared with areas with less or no impact (zones II and III, respectively). Significantly greater water content (p < 0.05) was found within the cartilage of zone I compared with zones II and III. CONCLUSIONS: Significant and possibly irreversible articular cartilage damage occurs after a single high-energy impact load.

Minimally invasive plate osteosynthesis of distal fractures of the tibia.

Minimally invasive plate osteosynthesis of distal tibial fractures is technically feasible and may be advantageous in that it minimizes soft tissue compromise and devascularization of the fracture fragments. The technique involves open reduction and internal fixation of the associated fibular fracture when present, followed by temporary external fixation of the tibia until swelling has resolved. Subsequent limited, but open reduction and internal fixation of the articular fragments when displaced followed by minimally invasive plate osteosynthesis of the tibia utilizing precontoured tubular plates and percutaneously placed cortical screws is performed. The semitubular plate was chosen because it adapts more easily to the bone contours than the stiffer small fragment LC-DCP does. Twenty patients (age 25-59 years) with unstable intraarticular or open extraarticular fractures have been treated including 12 A-type, 1 B-type and 7 C-type fractures according to the AO classification. Two fractures were open (both Gustilo Type I). Closed soft tissue injury was graded according to Tscherne with 3 type C0, 7 type C1, 7 type C2 and 1 type C3. All fractures healed without the need for a second operation. Time to full weight-bearing averaged 10.7 weeks (range 8-16 weeks). Two fractures healed with > 5 degrees varus alignment and 2 fractures healed with > 10 degrees recurvatum. No patient had a deep infection. The average range of motion in the ankle for dorsiflexion was 14 degrees (range 0-30 degrees) and plantar flexion averaged 42 degrees (range 20-50 degrees). With longer follow-up and a larger number of patients, the authors feel confident that the minimally invasive technique for plate osteosynthesis for the treatment of distal tibial fractures will prove to be a feasible and worthwhile method of stabilization while avoiding the severe complications associated with the more standard methods of internal or external fixation of those fractures.

Operative stabilization of fracture dislocations of the sacroiliac joint.

Posterior fracture dislocations of the sacroiliac joint (crescent fracture) represent a subset of lateral compression pelvic fractures. The crescent fracture consists of a posterior iliac wing fracture with extension into the sacroiliac joint and a dislocation of the inferior 1/2 of the sacroiliac joint. The posterior superior iliac spine remains firmly attached to the sacrum by the strong posterior ligaments. As a result of this combination of bony and soft tissue injury, the hemipelvis is rotationally unstable, but because the sacrospinous and sacrotuberous ligaments remain intact the involved hemipelvis is stable to vertically applied forces. Operative stabilization is necessary to restore articular congruity of the sacroiliac joint, pelvic stability, and to allow early mobilization of the patient. Stabilization of the pelvis may be achieved through either an anterior or a posterior approach with or without transarticular fixation. A posterolateral approach to the crescent fracture and a method of stabilization using extraarticular fixation, intertable lag screws and outer table antiglide plates are described. The results of using this technique in 22 patients are reviewed.

The crescent fracture: a posterior fracture dislocation of the sacroiliac joint.

Between October 1987 and August 1992, 22 patients with crescent fractures, a posterior fracture-dislocation of the sacroiliac joint, were admitted, treated, and available for review at Tampa General Hospital and The Hospital for Special Surgery. The purpose of the study was twofold: (a) to evaluate the incidence, severity, and pattern of associated injuries, and (b) to determine the efficacy of a treatment protocol using a posterior extrapelvic approach and extraarticular internal fixation. The study population was composed of 13 females and nine males; the average age was 25 years (range 10-52). Despite the fracture pattern resulting in a rotationally unstable hemipelvis, all patients were hemodynamically stable at the time of presentation. Fourteen patients (64%) had other associated injuries, including five (23%) with closed head injury. In all cases a posterior extrapelvic approach was used with an anatomic reduction of the fractured iliac wing and the sacroiliac joint dislocation. Stable extraarticular internal fixation was obtained using intertable lag screws and outer-table neutralization plates. All the fractures were clinically and radiographically healed within 8-10 weeks postoperatively, and there were no acute wound, neurologic, or vascular complications. One patient developed osteomyelitis of the iliac crest 6 months postoperatively.

Computerized tomography for the evaluation of posttraumatic multiplane deformities of the tibia.

Traditional assessment of posttraumatic multiplane deformities of the tibia includes radiographic evaluation with anteroposterior, lateral, and oblique radiographs for assessment of the coronal and sagittal deformities, and scanograms, teleroentgenograms, or orthoroentgenograms for the determination of limb length. Standard clinical measurements are used for the determination of rotational deformity. We report our technique and experience using a selected computerized tomography examination that provides accurate information necessary for the exact determination of the tibial deformity, and the preoperative planning of its correction. The technique is accurate, cost-effective, and safe, with less radiation exposure to the patient.

Stabilization of acetabular fractures in elderly patients.

Eighteen patients who were sixty years or older and had an acute displaced fracture of the acetabulum were managed with open reduction and internal fixation. The average age of the patients was sixty-seven years (range, sixty to eighty-one years). Nine fractures were a result of a motor-vehicle accident, and nine occurred in a fall. Nine patients had multiple associated injuries, and most (sixteen patients) had other complex acetabular fractures. All of the patients had open reduction and internal fixation with either the ilioinguinal approach (thirteen patients) or the Kocher-Langenbeck approach (five patients). All patients were managed postoperatively with early mobilization and physical therapy. All fractures united, and only one patient had a partial loss of reduction. Four patients who had a concentric reduction had a gap of as much as three millimeters in the articular surface due to comminution of the fracture. The complications included two pulmonary emboli, which resolved with anticoagulation, and one undetected intra-articular fragment, which led to an additional operation. No infections or iatrogenic nerve injuries were noted. Seventeen of the eighteen patients were followed for at least two years (average, thirty-one months). These patients had an average Harris hip-score of 90 points postoperatively. The treatment was regarded as having failed in only one patient. Open reduction and internal fixation of selected displaced acetabular fractures in the elderly can yield good results and may obviate the need for early and often difficult total hip arthroplasty.

Indirect reduction and percutaneous screw fixation of displaced tibial plateau fractures.

Indirect reduction and percutaneous screw fixation were attempted in 20 displaced tibial plateau fractures in 20 patients. Closed, indirect reduction was successful in 18 fractures; two others, both Schatzker type II fractures, required open reduction. The 18 fractures were followed for an average of 16.2 months (range, 12-24 months). Of the fractures successfully reduced with indirect techniques, 13 were reduced anatomically (72.2%), and five were considered nonanatomic (27.8%). Four of the five fractures with a nonanatomic reduction were type II fractures. Clinically, there were six excellent (33%), 10 good (56%), and two fair (11%) results. No fracture lost reduction; no patient developed an infection. Indirect techniques could effectively reduce only split fragments. Depressed fragments could not be reduced reliably with either ligamentotaxis or percutaneous elevation with a tamp. There was no correlation between radiographic reduction and clinical outcome. It did not matter whether two, three, or four screws were used to stabilize the fracture.

Orthopaedic manifestations of Rett syndrome.

We reviewed nine patients with Rett syndrome, a progressive encephalopathy that is being diagnosed more frequently in the United States. It occurs in females, causing mental deterioration, autistic behavior, and classic hand-wringing motion. The orthopaedic manifestations include scoliosis, lower extremity contracture, and coxa valga. Bracing and surgery are indicated to prevent or correct deformity and maintain ambulation.