Physical therapists often help patients feel how much weight they should place on the foot up through the leg after surgery. Limiting weight-bearing is important after some surgical procedures. For optimal healing, tissue must be protected and shouldn’t be overloaded. This is very important after autologous chondrocyte implantation (ACI).
ACI is a way to remove normal cartilage cells from the patient’s joint and grow new cells from them in the lab. The new cells are used to repair a defect (hole) in the surface of the joint. The postoperative rehab program starts off with limited and controlled weight-bearing.
There are a variety of ways to help the patient limit weight-bearing. Limb-load monitors, pressure insoles, and force monitoring platforms are possible but not always available. Using a bathroom scale to approximate the allowed weight is the easiest and least expensive method. But how accurate is this approach?
In this study, scientists use a standard bathroom scale to train patients to put partial weight on the leg after ACI. Each patient was given proper instructions and training first. Everyone was taught how to put 20, 40, 60, and 80 per cent of their body weight on the leg using a bathroom scale. In a typical rehab program, weight-bearing is gradually increased over a period of five to eight weeks. A forearm crutch is used on the opposite side to help offload weight.
In this program, patients must learn, retain, and reproduce the desired load while standing and walking. After practicing each of these weight loads, a force platform was used to measure ground reaction forces. Ground reaction forces refer to the force that goes through the foot, up the leg, and to the knee. Seven days later, everyone was re-assessed.
The researchers compared actual weight-bearing to the levels used during training. Pain levels and frequency were also monitored. They found that everyone used more body weight than prescribed or expected. This was true at all levels of weight-bearing and across all trials.
Accuracy was better after seven days, but still more than desired. The greatest improvement over the seven-day period was seen in the group applying 20 per cent of body weight. In general, accuracy did improve as more weight was allowed. In other words, greater accuracy occurred at 80 per cent weight bearing compared with 20 per cent.
The authors point out that there could be many other factors affecting the success of accurate weight-bearing. The role of pain, swelling, and muscle weakness has not been investigated. Mental state and physical fragility after surgery must also be taken into consideration. And we don’t really know what the long-term effects of weight-bearing are on cartilage protection and development of repair tissue.
For now, it is advised that until further research is done to answer these questions, it may be best to provide patients with more weight-bearing training after ACI. This is especially true for patients who are expected to place low loads (e.g., 20 per cent of body weight) using a touch toe technique. The success of the ACI may depend on it.
Further studies are needed to identify how the graft is affected by progressive weight-bearing programs. Is accuracy of weight-bearing even needed to prevent overloading the healing tissue? And if so, for how long? One week? Six weeks? The information gained from this type of research could be applied to patients after other orthopedic surgery affecting the joints of the lower extremity.