Effects of the deep anterior oblique and dorsoradial ligaments on trapeziometacarpal joint stability.

PURPOSE: Osteoarthritis of the trapeziometacarpal (TMC) joint of the thumb affects as many as 25% of postmenopausal women and 5% of middle-aged men. This study investigated the relative contribution of the dorsoradial ligament (DRL) and the deep anterior oblique ligament (dAOL) to the stability of the TMC joint. This knowledge will improve our understanding of the pathomechanics of osteoarthritis at the base of the thumb and may help to design novel reconstructive surgical procedures. METHODS: Seventeen intact cadaver hands were dissected to reveal the DRL and dAOL. Either the DRL or dAOL was transected randomly, physiologic muscle loads were applied to simulate lateral key pinch or thumb opposition, or a 3-dimensional magnetic tracking system was used to record the position of the thumb metacarpal relative to the trapezium. The differences in the 3-dimensional positions between the control and transected states were determined. RESULTS: In lateral pinch, transection of the DRL resulted in a mean increased 3-dimensional translation of 1.3 mm, whereas transection of the dAOL resulted in a mean increased 3-dimensional translation of 0.6 mm. Statistically significant 2-dimensional findings in lateral pinch after transecting the DRL or dAOL included an increased palmar subluxation of 0.3 mm and 0.2 mm, an increased radial (1.0 mm) and ulnar (0.3 mm) translation, and an increased pronation of 4.1 degrees and 2.4 degrees, respectively. In thumb opposition, transection of the DRL resulted in a mean increased 3-dimensional translation of 1.0 mm, whereas transection of the dAOL resulted in a mean increased 3-dimensional translation of 0.5 mm. CONCLUSIONS: In most degrees of freedom of metacarpal movement relative to the trapezium, the DRL is relatively more important than the dAOL in providing stability to the TMC joint.

Pain relief in knee osteoarthritis reduces the propensity to trip on an obstacle.

The pain associated with knee osteoarthritis (OA) has been shown to lead to an increased propensity to trip on an obstacle. Pain-relieving intra-articular injections are widely utilized in the treatment of knee OA. This study examined the effects of pain-relieving intra-articular knee injections on the ability to avoid contacting a suddenly appearing obstacle in patients with knee OA. Obstacle avoidance success rates, pain, body mass index, visual acuity, contrast sensitivity, depth perception, and single-leg stance duration were evaluated in nine patients with painful osteoarthritis of the knee and 14 age-matched healthy control subjects. Obstacle avoidance success rates, pain, and single leg stance duration were tested a second time in the patients with knee OA after they received their injections, which contained a fast-acting local anesthetic to provide rapid pain relief. After receiving the pain-relieving knee injections, patients with knee OA had 48% less pain and were 31% more successful in avoiding stepping on the obstacle. However, after receiving the injection, the obstacle avoidance success rates remained 20% less than those of the healthy controls. The results of this study suggest that knee pain-relief can decrease the propensity of people with painful knee OA to trip and fall over an obstacle. However, pain-relief alone did not return the patients with knee OA in this study to a disease-free risk of tripping.

Anatomy of the coronoid process.

PURPOSE: Coronoid injuries are classified according to the size of the coronoid fracture. The purpose of this study was to provide a detailed anatomic description of the coronoid process, with specific focus on the coronoid height, the coronoid width, and the olecranon-coronoid angle. METHODS: Thirty-five cadaveric arms were dissected. All soft tissue was removed and the ulna was disarticulated from the humerus, radius, and the carpal bones. A 3-dimensional digitizing system was used to locate 19 anatomic landmarks on each specimen. By using the 3-dimensional coordinates of the landmarks, the coronoid heights, proximal ulnar widths, and olecranon-coronoid angles were determined. RESULTS: The coronoid height, with its base defined by the trough of the trochlear notch and the slope change of the distal coronoid process, measured 15 mm and was 42% of the ulnar height. The coronoid height, with its base defined by the transverse groove of the sigmoid notch at the guiding ridge and the distal insertion of the brachialis muscle, measured 15 mm and was 43% of the ulnar height. The olecranon-coronoid angle ranged between 33 degrees and 38 degrees . CONCLUSIONS: For lateral radiographic classification of coronoid fractures, coronoid height is best defined by the trough of the trochlear notch and the slope change of the distal coronoid process. For anatomic studies, coronoid height is best defined by the transverse groove of the sigmoid notch at the guiding ridge and the distal insertion of the brachialis muscle. The olecranon-coronoid angle is best defined by the angle formed by the lines from the olecranon tip through the coronoid tip and through the slope change of the distal coronoid process. The coronoid anatomy measurements reported in this study may help to improve coronoid fracture classification.

Effects of a UCBL orthosis and a calcaneal osteotomy on tibiotalar contact characteristics in a cadaver flatfoot model.

BACKGROUND: A flatfoot deformity alters the contact characteristics of the ankle joint, shifting the location of articulation posterolaterally, increasing pressure, and decreasing the contact area within the ankle. These changes may explain the pattern of articular degeneration and subsequent angulation observed in a long-standing adult acquired flatfoot. Corrective orthoses and surgical reconstruction have been used to realign pes planovalgus feet, but the effects of these treatments on tibiotalar contact characteristics are unknown. We hypothesized that realignment of a flatfoot with either corrective orthosis or surgical reconstruction would restore the contact characteristics of the ankle to the intact state. METHODS: The mean value of the contact area, contact pressure, peak contact pressure, and the relative locations of the global contact area and peak pressure within the ankle joint were determined from imprints created on pressure sensitive film for a series of cadaver lower limbs subjected to a weightbearing load in simulated midstance phase of gait. Each limb was loaded sequentially under four conditions: intact, flatfoot, flatfoot realigned with UCBL orthosis, and flatfoot realigned with a medial translational osteotomy of the calcaneus. RESULTS: The use of the UCBL orthosis and calcaneal osteotomy altered the contact characteristics of the ankle when compared with the flatfoot condition. Both interventions significantly decreased the mean global contact pressure from the flatfoot value, with the orthosis, demonstrating a significantly greater correction than the osteotomy. The orthosis also significantly reduced the peak contact pressure from the flatfoot value. Both interventions significantly corrected the lateral shift of the center of the peak contact pressure from the flatfoot value. The shift in the center of the global contact area approached significance when the orthosis was compared with the flatfoot. CONCLUSIONS: The changes observed in the magnitude and location of the mean and peak pressures indicate that the UCBL orthosis and calcaneal osteotomy altered hindfoot alignment to significantly influence tibiotalar contact characteristics. The results further suggest that the UCBL orthosis corrected ankle malalignment better than the calcaneal osteotomy in an adult acquired flatfoot. This study provides biomechanical data to support the clinical impression that realignment of the hindfoot corrects the pathologic tibiotalar contact characteristics associated with an adult acquired flatfoot. The results support the conclusion that the clinical management of a pes planovalgus foot with a UCBL orthosis or a medial translational osteotomy of the calcaneus may avert the onset of pantalar disease seen with late-stage posterior tibial tendon dysfunction.

Bilateral total knee arthroplasty increases the propensity to trip on an obstacle.

Tripping over an obstacle is the most frequent cause of falls. We examined the effects of total knee arthroplasty on obstacle avoidance success rates in older adults. Obstacle avoidance success rates, body mass index, visual acuity, contrast sensitivity, depth perception, and single-leg stance duration were evaluated in 29 subjects who had bilateral total knee arthroplasties (age range, 72.6 +/- 5.4 years) and 27 age-matched healthy control subjects (age range, 70.6 +/- 5.5 years). The patients who had total knee arthroplasties had a lower obstacle avoidance success rate, lower single-leg stance duration, and greater body mass index than control subjects. Age, contrast sensitivity, and depth perception were not different between patients who had total knee arthroplasties and control subjects. Obstacle avoidance success rates decreased linearly as single-leg stance duration decreased in the control group and across all groups, but not in the group that had total knee arthroplasties. Linear relationships between obstacle avoidance success rates and body mass index existed for all subjects but not for the group that had total knee arthroplasties or the control group individually. Total knee arthroplasty reduces obstacle avoidance success rate, suggesting that persons who have total knee arthroplasties have an increased propensity to trip on an obstacle and fall. Increased body mass index and decreased single-leg stance duration in patients who have total knee arthroplasties are associated with a decreased obstacle avoidance success rate.

Osteoarthritis of the knees increases the propensity to trip on an obstacle.

Tripping on an object is the most frequent cause of falls. We examined the effects of painful osteoarthritis of the knee on obstacle avoidance success rates in older adults. Obstacle avoidance success rates, pain, body mass index, visual acuity, contrast sensitivity, depth perception, and single-leg stance duration were evaluated in 17 patients with painful osteoarthritis of the knees (age range, 59.6 +/- 8.1 years) and 14 age-matched healthy control subjects (age range, 61.1 +/- 10.0 years). The patients with osteoarthritis of the knees had a 37% lower obstacle avoidance success rate, a 54% lower single-leg stance duration, and a 24% greater body mass index than the control subjects. Age, visual acuity, contrast sensitivity, and depth perception were not different between the two groups. Obstacle avoidance success rates and single-leg stance durations decreased linearly as pain increased in the patients with osteoarthritis of the knees. Obstacle avoidance success rates also decreased linearly as single-leg stance duration decreased in the patients with osteoarthritis of the knees. Osteoarthritis of the knees reduced obstacle avoidance success rates, supporting epidemiologic studies that have found osteoarthritis to be a risk factor for falls. This study showed that pain associated with osteoarthritis of the knees increased the propensity to trip on an obstacle (the greater the pain the greater the propensity to trip and fall) and underscores the importance of treating pain associated with osteoarthritis.

Effects of the adductor pollicis and abductor pollicis brevis on thumb metacarpophalangeal joint laxity before and after ulnar collateral ligament reconstruction.

PURPOSE: The intrinsic muscles and ulnar capsuloligamentous structures (UCLS), which consist of the ulnar collateral ligament (UCL), accessory UCL, dorsal capsule, and volar plate of the thumb metacarpophalangeal (MCP) joint are important for controlling the motion and stability of the MCP joint during pinch. The purpose of this cadaveric study was to determine the effects of the adductor pollicis (AdP) and abductor pollicis brevis (APB) on the 3-dimensional MCP joint laxity before transection of the UCLS and after reconstruction of the UCL and repair of the dorsal capsule. METHODS: Loads were applied to the flexor pollicis longus (FPL) alone, to the AdP and FPL in combination, and to the APB and FPL in combination in 11 cadavers. This was done in the intact joint after the UCLS were transected and after the UCL was reconstructed for flexion angles of 0 degrees, 15 degrees, 30 degrees, and 45 degrees. The spatial positions of the proximal phalanx and the metacarpal of the MCP joint were measured with a 6-degrees-of-freedom digitizing system. RESULTS: In the intact joint combined loading of the AdP and FPL did not affect the position of the proximal phalanx. Combined loading of the APB and FPL changed the position of the phalanx from an ulnar to a radial shift and from an ulnar to a radial deviation and it increased pronation. After transection of the UCLS combined loading of the FPL and AdP increased supination of the MCP joint and combined loading of the FPL and APB increased radial shift, radial deviation, and pronation of the joint. Reconstruction of the UCL restored normal laxity to the MCP joint. CONCLUSIONS: The AdP failed to affect MCP joint motion. The ABP produced a radial shift and radial deviation of the MCP joint and increased pronation of the thumb. Transection of the UCLS increased joint laxity for each of the combined loadings and reconstruction of the UCL restored normal laxity to the MCP joint.

Effects of knee pain relief in osteoarthritis on gait and stair-stepping.

Osteoarthritic knee pain affects patient mobility. Relief of knee pain in osteoarthritis has been reported to increase loading of the knee during gait, but it is unknown whether such pain relief enhances knee loading during more demanding activities such as stair-stepping. The gait of 19 patients and stair-stepping of 14 patients with painful medial compartment osteoarthritis of the knee was assessed before and after pain-relieving intraarticular injection of the knee and compared with those of 21 healthy control subjects. There were significant increases in gait velocity, cadence, maximum external knee adduction moment (indicating increased loading in the medial compartment of the knee), and maximum external hip adduction and ankle abduction moments immediately after the injection. With the exception of velocity and ankle abduction moment, these variables were returned to levels that were not statistically different from those of the control subjects. However, no significant differences were found during stair-stepping in the external adduction-abduction moments about the knee, hip, or ankle after injection. Furthermore, the postinjection magnitudes of these variables during stair-stepping were significantly less than those of the controls. Therefore, although the relief of knee pain is sufficient to enhance gait function in osteoarthritis of the knee, it is insufficient to enhance stair-stepping function.

The effects of walking speed on obstacle crossing in healthy young and healthy older adults.

The effects of walking speed and age on the peak external moments generated about the joints of the trailing limb during stance just prior to stepping over an obstacle and on the kinematics of the trailing limb when crossing the obstacle were investigated in 10 healthy young adults (YA) and 10 healthy older adults (OA). The peak hip and knee adduction moments in OA were 21-43% greater than those in YA (p

The effects of early rollback in total knee arthroplasty on stair stepping.

We investigated the effects of early compared with late (ie, in flexion) rollback on quadriceps efficiency during stair stepping. We studied 10 patients with the IB II (Zimmer, Warsaw, IN) total knee arthroplasty (TKA), designed to enforce rollback at 73 degrees of knee flexion; 9 patients with the Maxim PS (Biomet, Inc, Warsaw, IN) TKA, designed to enforce rollback between 20 degrees and 30 degrees of flexion; 8 patients with the TRAC PS (Biomet, Inc, Warsaw, IN) mobile bearing TKA, designed to enforce rollback at 8 degrees of flexion; and 21 healthy control subjects during stair stepping. We measured the external knee flexion moments, which must be largely balanced by quadriceps force acting over the quadriceps lever arm, as indicators of quadriceps efficiency. The peak external knee flexion moment generated by the IB II patients during stair stepping was 12.4% and occurred at 65 degrees of knee flexion. This moment was significantly less (P=.006) than the peak moment, 17.6%, generated by the healthy controls. Knee flexion for the IB II patients did not reach 73 degrees, and rollback was not enforced until after the peak moment (ie, maximum demands on the quadriceps) had been attained. The peak moments generated by the TRAC PS patients, 14.2%, and Maxim patients, 14.8%, were not significantly different from that of the controls. These results suggest that early as compared with late rollback returns more normal quadriceps efficiency during stair stepping.

A dynamic model for simulating a trip and fall during gait.

The purpose of this study was to develop an analytical model to simulate a trip and fall during gait. The human body was modeled as a 12 degree-of-freedom linkage system. The kinematics of the lower extremity for one cycle of gait were obtained for a healthy subject using an optoelectronic three-dimensional data acquisition system. Inverse dynamics was used to compute the moments about the hip, knee and ankle joints of the lower extremity. These moments were then used as input actuators to the joints in to a forward dynamics model to simulate the swing phase of gait from toe-off to heel-strike. An optimization procedure to minimize errors associated with the computed experimental torque was applied to correct for mathematical instability. An experiment was performed to measure the three-dimensional foot--obstacle contact force for a healthy subject tripping on an obstacle during gait. The contact force was applied to the swing limb of the forward dynamics model for 0.09 s beginning at 0.04 s after toe-off. Tripping on an obstacle followed by a muscle-relaxed fall was simulated. The simulation results were visualized with animation software.

The effects of removal and reconstruction of the anterior cruciate ligament on the contact characteristics of the patellofemoral joint.

Seven cadaveric knees were used to investigate the effects of removal and reconstruction of the anterior cruciate ligament with a bone-patellar tendon-bone graft on contact characteristics of the patellofemoral joint during physiologic levels of quadriceps muscle loads at 30 degrees, 60 degrees, and 90 degrees of knee flexion. Loads were applied to the quadriceps tendon to equilibrate externally applied flexion moments equivalent to one-third of values for maximum isometric extension moments. Patellofemoral contact areas and pressures were measured using pressure-sensitive film. Excision of the anterior cruciate ligament resulted in significant decreases in the total patellofemoral contact area by as much as 94 mm2 (68%), the medial facet contact area by as much as 55 mm2 (93%), the combined average contact pressure by 0.7 MPa (21%), the medial facet average contact pressure by 2.3 MPa (70%), the combined peak contact pressure by 3.0 MPa (38%), and the medial facet peak contact pressure by 5.4 MPa (76%), all at 30 degrees of knee flexion. Excision of the anterior cruciate ligament also resulted in significant decreases in total, medial facet, and lateral facet patellofemoral contact areas at 60 degrees and 90 degrees of knee flexion. Intraarticular reconstruction returned these to levels not significantly different from those of the intact knee.