Gait analysis after total hip replacement with hip resurfacing implant or Mallory-head Exeter prosthesis: a randomised controlled trial.

A key to the analysis of function after total hip replacement (THR) is the ability to identify gait adaptations specific to design features and surgical procedures. In a randomised controlled design, we evaluated the mechanics of gait after THR with a hip resurfacing system or conventional prosthesis. We also investigated whether gait adaptations returned to normal postoperatively. Similar improvements in mechanics of gait were found, except for peak abductor moments, which improved more in the conventional group. Gait speed increased significantly, but with no differences between groups. The increase in walking speed was reflected as significant improvement within groups in most kinematic and kinetic variables. Significant differences between the operated and non-operated hip were seen in all patients, but with no difference between groups. Mean curves of joint angle profiles and moments in all anatomical planes during a gait cycle revealed that gait impairment persisted with no differences between the conventional prosthesis and the resurfacing system.

Self-reported functional outcome after primary total hip replacement treated with two different periopera-tive regimes: a follow-up study involving 61 patients.

BACKGROUND AND PURPOSE: Fast-track surgery has been reported to improve rehabilitation outcome after major surgery, with length of hospitalization and muscle strength as outcome measures. We assessed the effect of optimization of perioperative care during admission on self-reported functional outcome, and compared patient status 6 months after THR with an age-matched healthy cohort. PATIENTS AND METHODS: 79 THR patients were randomized to optimized perioperative care (OPC) or conventional perioperative care (CPC). 61 patients fulfilled the requirements of the study protocol. Endpoint outcome was measured by SF-36 and WOMAC. To compare functional outcome in the THR group with that in healthy controls, we used data from a representative sample of 4,098 non-institutionalized Danish adults collected by the Danish National Institute of Public Health. RESULTS: We found similar improvements in SF-36 and WOMAC scores for the OPC and CPC groups postoperatively, except for the total WOMAC score and the WOMAC subscore "function"-in which the CPC group did statistically significantly better. The OPC and CPS groups had similar score levels. 6 months after surgery, THR patients scored higher overall in the general health subscale and lower in three physical subscales of SF-36 compared to age-matched healthy controls. Interpretation We found no evidence for the effect of optimization strategies during admission on self-reported functional outcome after THR. Although THR patients improved considerably after treatment, their physical status remained below the level of the healthy controls. Our results may indicate that the potential for functional improvement in THR patients is not fully realized, but this must be studied further.

"To whom do the results of this trial apply?" External validity of a randomized controlled trial involving 130 patients scheduled for primary total hip replacement.

BACKGROUND: Although the randomized controlled trial (RCT) is regarded as the gold standard for evaluation of the effect of an intervention, its external validity has been questioned. RCTs cannot be expected to produce results that are directly relevant to all patients and all settings, but they should at least allow patients and clinicians to judge to whom trial results can reasonably be applied. We assessed the external validity of an RCT investigating the efficacy of a fast-track program after total hip replacement. METHODS: 130 patients were identified as potential participants.18 patients were excluded, 33 enrolled patients declined to participate, and 79 patients were enrolled and randomized. We studied the distribution of preoperative characteristics and postoperative clinical variables in these 3 groups. RESULTS: A significant difference was found in both preoperative characteristics and clinical outcome variables. The non-consenters were older, less healthy, and needed more help from the home care system. Furthermore, they were hospitalized longer and were more often transferred to a rehabilitation ward. INTERPRETATION: Our findings demonstrate the importance of patient inclusion criteria in RCTs. Moreover, they may account for the lack of reproducibility of RCT results in clinical practice dealing with fast-track programs.

The exploitation of an ant-defended host plant by a shelter-building herbivore.

Larvae of a Polyhymno species (Lepidoptera: Gelechiidae) feed on the ant-defended acacia, Acacia cornigera, in the tropical lowlands of Veracruz, Mexico. Polyhymno larvae construct sealed shelters by silking together the pinna or pinnules of acacia leaves. Although larval density and larval survival are higher on acacias not occupied by ants, shelters serve as a partial refuge from the ant Pseudomyrmex ferruginea (Hymenoptera: Formicidae), which defends A. cornigera plants; thus, shelters provide Polyhymno larvae access to an ant-defended host plant. P. ferruginea ants act as the primary antiherbivore defense of A. cornigera plants, which lack the chemical and mechanical defenses of non-ant-defended acacias. Thus, defeating the ant defense of A. cornigera provides Polyhymno larvae access to an otherwise poorly defended host plant. Damage caused by Polyhymno larval feeding reaches levels which can kill A. cornigera plants.