Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis.

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 65°-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions. A ligament-tuning process minimised kinematic differences between the robotically loaded cadaver specimen and the finite element (FE) model. The model was validated by measured intra-articular force and pressure measurements. Percent full scale error between FE-predicted and in vitro-measured values in the medial and lateral compartments were 6.67% and 5.94%, respectively, for normalised peak pressure values, and 7.56% and 4.48%, respectively, for normalised force values. The knee model can accurately predict normalised intra-articular pressure and forces for different loading conditions and could be further developed for subject-specific surgical planning.

Limb lengthening in children with Russell-Silver syndrome: a comparison to other etiologies.

INTRODUCTION/BACKGROUND: Russell-Silver syndrome (RSS) is the combination of intrauterine growth retardation, difficulty feeding, and postnatal growth retardation. Leg length discrepancy (LLD) is one of four major diagnostic criteria of RSS and is present in most cases. We aimed to ascertain whether pediatric RSS patients will adequately consolidate bony regenerate following leg lengthening. MATERIALS AND METHODS: We retrospectively reviewed pediatric RSS patients who underwent limb lengthening and compared them to a similar group of patients with LLD resulting from tumor, trauma, or congenital etiology. The primary outcome measurement was the bone healing index (BHI). RESULTS: The RSS group included seven lengthened segments in five patients; the comparison group included 21 segments in 19 patients. The groups had similar lengthening amounts (3.3 vs. 3.9 cm, p = 0.507). The RSS group healed significantly faster (lower BHI) than the control group (BHI 29 vs. 43 days/cm, p = 0.028). Secondary analysis showed no difference between RSS and trauma patients in terms of the BHI (29 vs. 31); however, the BHI of the RSS group was significantly lower than both of the other congenital etiologies (29 vs. 41, p = 0.032) and tumor patients (29 vs. 66, p = 0.019). The RSS patients had fewer and less significant complications than the controls. DISCUSSION: The limb lengthening regenerate healing of RSS patients is faster than the healing of patients with other congenital etiologies and tumor patients, and is as fast as the regenerate healing of patients with posttraumatic LLD. Although all RSS patients were treated with human growth hormone (hGH), we are unable to isolate the hGH contribution to the regenerate bone healing. We conclude that RSS patients can have safe limb lengthening.

The evolution of femoral shaft plating technique.

There has been an evolution in the AO/Association for the Study of Internal Fixation plating technique during the past 3 decades that includes the use of longer plates and fewer plate screws, fewer lag screws outside the plate, fewer unicortical screws at the plate periphery, and greater use of the 95 degrees blade plate to achieve balanced fixation of proximal and distal shaft fractures. These changes reflect an evolving technique of plate osteosynthesis that emphasizes indirect reduction techniques, biologic internal fixation, and improved biomechanics. Outcome data suggest that there has been an improvement with time that is reflected by shorter time to union, a decrease in the frequency of implant failures, delayed unions, nonunions, malunions, number of reoperations, and in overall rate of failure. The best predictor of success was the length of plate by logistic regression analysis. With the evolution of plating techniques and a greater emphasis on biology of fracture healing, the incidence of complications and failures has decreased after femoral shaft plating. Plate osteosynthesis of the femoral shaft is particularly advantageous in many situations and can be quite successful (87% success rate in Group III).

Ganglion cysts of the lower extremity: an analysis of 54 cases and review of the literature.

This article reviews 54 consecutive patients with lower extremity ganglion cysts that were surgically removed and histologically confirmed at the Hospital for Special Surgery from 1981 to 1993. Lower extremity ganglia were more common among women. Patients' ages ranged from 13 to 80 years, with the fifth and sixth decades being the most common. Size of the cysts ranged from 3 cm to 10 cm (average: 2.9 cm). Thirty-six (67%) patients had ganglion cysts of the foot and ankle, and 18 (33%) patients had ganglion cysts of the knee area. Four (7%) patients had intraosseous ganglia located in the proximal tibia, patella, and the first metatarsal head. Follow-up data of 40 (74%) patients at an average of 5.9 years (range: 1 to 12.5 years) were obtained. Satisfaction was reported by 83% of patients. Recurrence was seen in 10% of patients, and a report of no or mild pain was given by 86% of the group. Patients who underwent revision ganglion excision had inferior results. Only 25% reported satisfaction and 50% reported no or mild pain. Patients who underwent curettage of an intraosseous ganglion appeared to have superior results. All patients reported satisfaction and no or mild pain. The performance of a concomitant surgical procedure, the anatomic region of the ganglion, or type of postoperative immobilization did not appear to affect the outcome.

Osteonecrosis of the knee following arthroscopic laser meniscectomy.

An unusual case of osteonecrosis of the knee following an arthroscopic laser meniscectomy is presented. The unusual presentation of the osteonecrosis and the chronology suggest that the osteonecrosis of the knee resulted from damage to the articular cartilage and subchondral bone at the time of the arthroscopic laser meniscectomy.