Predictions on preserving bone mass in knee arthroplasty with bisphosphonates.

Using a computational model of bone adaptation, we investigated the long-term ability of bisphosphonates to minimize proximal bone loss that is associated with stress shielding in the tibia after long-stemmed total knee arthroplasty (TKA). When invoking bisphosphonate effects, the remodeling activity was suppressed, and the resorption size was reduced. Compared with the untreated simulation, bisphosphonate slowed the rate of bone loss after TKA (42% reduction in bone loss at 1 year). Activating the drug 3 months before the surgery reversed bone loss associated with the reduction in such activities as walking, but it did not provide any substantial benefit in the long-term. Late bisphosphonate treatment did not reverse the bone loss that occurred 3.5 years after TKA, although it preserved 3% of bone normally lost without treatment.

Patient satisfaction and outcome after microfracture of the degenerative knee.

Satisfaction and functional outcome was measured in 81 patients who were treated arthroscopically with microfracture for isolated degenerative lesions of the knee. Average patient age was 49 years (range: 40-70 years) and average degenerative lesion measured 229.5 mm2 (range: 25-2000 mm2). Patients were evaluated at average 2.6-year follow-up (range: 2-5 years). All subjective parameters measured (pain, swelling, limping, walking, stairs, sport level, and activities of daily living) demonstrated significant improvement over preoperative status (P<.003). Lysholm score improved from 53.8 to 83.1 (P<.001), and mean Tegner Activity Scale score improved from 2.9 to 4.5 (P<.05). No significant association was noted between Lysholm improvement and gender or age. Significant improvement in mean Lysholm score was noted for lesions in all three knee compartments. Thirteen patients required repeat arthroscopy within 5 years of initial microfracture for lysis of adhesions. Five patients required revision microfracture to a previously treated lesion or total knee arthroplasty at an average of 23 months (range: 5-36 months) from the initial microfracture. Microfracture is an efficacious surgical option for the treatment of degenerative chondral lesions of the knee. The modest rate of failure and need for arthroscopic lysis of adhesions reflects the challenge of joint-sparing arthroscopic surgery in the degenerative knee.

Long stemmed total knee arthroplasty with interlocking screws: a computational bone adaptation study.

The ability of an interlocking screw fixation technique to minimize bone loss related to stress shielding in the tibia was investigated and compared to the abilities of cement and press-fit fixation. Full bony ingrowth has been associated with greater stress shielding than partial ingrowth; therefore, the effect of intimate bonding of the stem to bone on subsequent bone loss was also studied. A damage- and disuse-based remodeling theory was coupled with a two-dimensional finite element model of the tibia to predict changes in bone remodeling following long stemmed total knee arthroplasty (TKA) for four different fixation techniques (cement, press-fit, interlock with bony ingrowth, and interlock without bony ingrowth). Remodeling changes commenced with the model state variables--bone area fraction, mechanical stimulus, damage, and remodeling activity--at steady-state values predicted by the intact tibia simulation. After TKA and irrespective of fixation technique, the model predicted elevated remodeling due to disuse, in which more bone was removed than replenished. In regions below the tibial tray and along the cortices, the interlocking stem with full bony ingrowth and the cemented stem caused the least amount of bone loss. An interlocking stem with a smooth, matted finish did not reduce the bone loss associated with interlocking fixation.

Operative stabilization of supracondylar femur fractures above total knee arthroplasty: a comparison of four treatment methods.

Periprosthetic fractures of the distal femur above a total knee arthroplasty present a challenging surgical problem for orthopedic surgeons. Numerous operative and nonoperative treatment options exist including casting, Rush rods, supracondylar nails, and plate fixation. Potentially significant complications are associated with all current treatment alternatives. Plate or nail constructs frequently achieve limited distal fixation, leading to loss of fixation and varus angulation. This complication was not observed with the Less Invasive Stabilization System (LISS). In addition, our early results demonstrate the superiority of LISS treatment with low infection rates, no requirement for acute bone grafting, and secure fixation allowing for immediate postoperative mobilization. LISS fixation may offer a superior surgical treatment option for periprosthetic distal femur fractures.

Outcomes of microfracture for traumatic chondral defects of the knee: average 11-year follow-up.

PURPOSE: In this study, we measured functional outcomes of patients treated arthroscopically with microfracture for full-thickness traumatic defects of the knee. TYPE OF STUDY: A case series of patients with 7 to 17 years' follow-up. METHODS: Between 1981 and 1991, a total of 72 patients (75 knees) met the following inclusion criteria: (1) traumatic full-thickness chondral defect, (2) no meniscus or ligament injury, and (3) age 45 years and younger (range, 13 to 45 years). Seventy-one knees (95%) were available for final follow-up (range, 7 to 17 years). All patients completed self-administered questionnaires preoperatively and postoperatively. RESULTS: The following results were significant at the P <.05 level. Significant improvement was recorded for both Lysholm (scale 1 to 100; preoperative, 59; final follow-up, 89) and Tegner (1 to 10; preoperative, 3; final follow-up, 6) scores. At final follow-up, the SF-36 and WOMAC scores showed good to excellent results. At 7 years after surgery, 80% of the patients rated themselves as "improved." Multivariate analysis revealed that age was a predictor of functional improvement. CONCLUSIONS: Over the 7- to 17-year follow-up period (average, 11.3 years), patients 45 years and younger who underwent the microfracture procedure for full-thickness chondral defects, without associated meniscus or ligament pathology, showed statistically significant improvement in function and indicated that they had less pain.

Lumbar Spine Injuries in Military Parachute Jumpers.

Jumpers with lumbar spine injuries caused by bad landings had a high incidence of chip or slice fractures, but degenerative disk disease was unrelated to jumping injuries.