Lawrence A. Pottenger

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.

Knee laxity in symptomatic osteoarthritis

Twenty-two patients with primary osteoarthritis (OA) of the knee were studied to determine the effects of OA on laxity of the knee joint. Laxity was measured with a Genucom Knee Analysis System. Ten knees had mild OA (> 50% preservation of joint space). Fifteen knees had moderate OA (some preservation of joint space, but < 50%). Eighteen knees had severe OA (no joint space). A group of 18 knees from 9 healthy (asymptomatic) subjects of ages similar to those of the OA patients were used as controls. Compared to control knees, severe OA knees had less total anteroposterior (AP) translation (12.2 versus 6.6 mm, p < 0.025) and less total tibial rotation (79 versus 59 degrees, p < 0.01). Compared to early OA knees, knees with severe OA had 57% less average total AP translation (15.2 versus 6.6 mm, p < 0.01), 31% less total varus/valgus rotation (15 degrees versus 10.4 degrees, p < 0.016), and 26% less total internal/external tibial rotation (80.1 degrees versus 59 degrees, p < 0.007). These data indicate that osteoarthritic knees tend to have less laxity than normal knees, probably because of a combination of contracture of the ligaments and pressure of osteophytes against ligaments and other capsular structures.

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.

Mechanical disruption of human patellar cartilage by repetitive loading in vitro

Plugs of cartilage and subchondral bone from patellae were subjected to cyclic compression consisting of rapid ramp loading for 0.3 seconds followed by a 2.7 second pause. At 1000 psi cyclic load, surface abrasion of the cartilage was noted at 250 cycles of compression. Primary fissures, which penetrated to the calcified cartilage, developed at 500 cycles. Secondary fissures, emanating from the primary fissures at 30 degrees-90 degrees angles, and penetrating to varying depths, were observed at 1000 cycles. Coalescence of fissures and undermining of cartilage fragments were noted at 8000 cycles. With greater loads, the same sequence of events occurred with fewer cycles except that primary fissures appeared before the surface was abraided. Fissure formation did not occur in specimens subjected to loads of 250 psi to 500 psi even if the superficial 100 micron of cartilage was removed and specimens were loaded for 120,860 cycles. The deeper layers of cartilage appear to be of prime importance in resisting fissure formation.

Cementless total hip arthroplasty in patients with steroid-induced avascular necrosis of the hip. A 62-month follow-up study.

Twenty cementless porous-coated primary total hip arthroplasties (THA) were performed on 15 patients, all of whom were diagnosed with steroid-induced avascular necrosis (AVN). The average age of the patients at the time of surgery was 45 years. Minimum follow-up period for all patients was 24 months (average follow-up period: 62 months). Patients were rated using the modified Harris hip score, as well as serial radiographs. The average hip score at follow-up examination was 88, with 17 of the 20 hips having good or excellent clinical results. No revisions of the prostheses were performed. Using radiographic criteria, 12 femoral components met the criteria for bone ingrowth, seven were considered stable with fibrous fixation, and one femoral component was loose. When good initial femoral component fit was achieved, bone ingrowth reliably followed. Three acetabular components showed migration on serial radiographs. A high rate of acetabular component wear and osteolysis was noted. Avascular necrosis has been shown to adversely affect the outcome of hip arthroplasty surgery. Previous studies of patients with advanced AVN undergoing cemented THA report a high incidence of component loosening. Literature on the results of cementless THA in this patient group is sparse. The study demonstrates encouraging clinical results for cementless THA in steroid-induced AVN. Reliable femoral component fixation occurred if a good initial component fit was achieved; however, long-term acetabular loosening and wear remain serious concerns.

Nonenzymatic glycation of cartilage proteoglycans: an in vivo and in vitro study

In this study we have investigated whether proteoglycans (aggrecan) are modified by nonenzymatic glycation as in collagen. Purified human aggrecan from osteoarthritic and normal human knee articular cartilage was assayed for pentosidine, a cross-link formed by nonenzymatic glycation, using reverse-phase HPLC. In addition, an in vitro study was done by incubation of purified bovine nasal cartilage aggrecan with ribose. Pentosidine was found in all the purified human aggrecan samples. 2-3% of the total articular cartilage pentosidine was found in aggrecan. Purified link protein also contained penosidine. The in vitro study led to pentosidine formation, but did not appear to increase the molecular size of the aggrecan suggesting that pentosidine was creating intramolecular cross-links. Similar amounts of glycation were found in osteoarthritic and normal cartilage. Like collagen, aggrecan and link proteins are crosslinked by nonenzymatic glycation in normal and osteoarthritic cartilage. Crosslinking could be reproduced, in vitro, by incubating aggrecan with ribose.

The TRAC PS mobile-bearing prosthesis: Design rationale and in vivo 3-dimensional laxity

Abstract We present a posterior stabilized mobile-bearing prosthesis, TRAC PS, which has congruent contact from full extension to full flexion, allows for freedom of internal-external rotation, and has an automatic posterior shift in tibiofemoral contact on the tibia to maximize the quadriceps lever arm in flexion. TRAC PS has 2 radii of curvature in the sagittal plane, 1 for the distal femoral condyles and 1 for the posterior femoral condyles, as does the normal knee. The distal and posterior femoral condyles articulate congruently in the inner tracks or the outer tracks of the polyethylene bearing, respectively. Anterior or posterior sliding of the femoral condyles on the bearing or of the bearing on the tibial tray cannot occur, providing inherent anterior and posterior stability. Three-dimensional knee laxity testing was performed on 17 patients from 12 months to 25 months after total knee arthroplasty with the TRAC PS and on 18 healthy control subjects of similar ages. Normal ligament balancing and normal internal-external rotational laxity were achieved with the TRAC PS prosthesis. Anterior and posterior laxity in the patients with TRAC PC was significantly reduced compared with that of the control subjects.

The Effects of the Rotating-Hinge Total Knee Replacement on Gait and Stair Stepping

We studied 7 younger and 5 older patients who had rotating-hinge total knee replacements, 10 patients who had semiconstrained total knee replacements, and 8 younger and 11 older healthy control subjects to determine the effects of the rotating-hinge device on gait and stair stepping. The younger patients with the rotating-hinge device had few significant differences from the younger control subjects during gait or stair stepping. The older patients with the rotating-hinge device had several significant differences from both the older control subjects and subjects with the semiconstrained device during gait and stair stepping. Nevertheless, the proportions of older patients with the 2 devices who were able to perform the step-on activity for the highest step were the same.

Proteoglycan extraction of sized cartilage particles

The relationship between cartilage thickness and proteoglycan extractability was examined. Bovine nasal cartilage slices (20, 100, and 500 micron thicknesses) were extracted with low-ionic-strength buffer and 4 M guanidine hydrochloride. The extractability of proteoglycans with both solutions depended on slice thickness. Thinner slices yielded greater amounts of proteoglycans. Sixty-three percent of the total cartilage uronic acid was extracted from 20-micron cartilage slices with low-ionic-strength buffer while only 7% was extracted for 500-micron slices. Each fivefold increase in cartilage surface area led to a threefold increase in uronic acid extraction with low-ionic-strength buffer. Extraction of proteoglycan aggregates was directly proportional to the cartilage surface area whereas extraction of non-aggregated proteoglycans, per surface area, increased with increasing cartilage thickness. These data are consistent with the hypothesis that proteoglycan aggregates are extracted mainly from the cartilage surface while non-aggregated proteoglycans diffuse from deep within the cartilage. Extraction with low-ionic-strength buffer occurred in two phases. There was an initial rapid loss of proteoglycans in which 1/3 to 1/2 of all proteoglycans eluting over 6 days were extracted during the first 30 min. Subsequent extraction was much slower with decreasing amounts extracted on each consecutive day. The initial rapid loss of proteoglycans was probably due to the steep osmotic-pressure gradient existing when the cartilage was placed in the low-ionic-strength buffer.

Paraxial macrodystrophia lipomatosa of the medial right lower limb

We report the orthopaedic management of a child with macrodystrophia lipomatosa of the medial aspect of the right lower limb. Bony and soft tissue overgrowth of the medial aspect of the lower limb resulted in valgus deformities at the subtalar joint, ankle, knee, and hip. The paraxial distribution, which has not been previously reported, suggests that the condition may be caused by alteration of somatic cells during limb bud development.