The Use of Low Frequency Pulsing Electromagnetic Fields in Patients with Painful Hip Prostheses

Role of pulsed electromagnetic fields after joint replacements

Although the rate of patients reporting satisfaction is generally high after joint replacement surgery, up to 23% after total hip replacement and 34% after total knee arthroplasty of treated subjects report discomfort or pain 1 year after surgery. Moreover, chronic or subacute inflammation is reported in some cases even a long time after surgery. Another open and debated issue in prosthetic surgery is implant survivorship, especially when related to good prosthesis bone ingrowth. Pulsed Electro Magnetic Fields (PEMFs) treatment, although initially recommended after total joint replacement to promote bone ingrowth and to reduce inflammation and pain, is not currently part of usual clinical practice. The purpose of this review was to analyze existing literature on PEMFs effects in joint replacement surgery and to report results of clinical studies and current indications. We selected all currently available prospective studies or RCT on the use of PEMFs in total joint replacement with the purpose of investigating effects of PEMFs on recovery, pain relief and patients’ satisfaction following hip, knee or shoulder arthroplasty. All the studies analyzed reported no adverse effects, and good patient compliance to the treatment. The available literature shows that early control of joint inflammation process in the first days after surgery through the use of PEMFs should be considered an effective completion of the surgical procedure to improve the patient’s functional recovery.

Biophysical stimulation of bone and cartilage: state of the art and future perspectives

INTRODUCTION

Biophysical stimulation is a non-invasive therapy used in orthopaedic practice to increase and enhance reparative and anabolic activities of tissue.

METHODS

A sistematic web-based search for papers was conducted using the following titles: (1) pulsed electromagnetic field (PEMF), capacitively coupled electrical field (CCEF), low intensity pulsed ultrasound system (LIPUS) and biophysical stimulation; (2) bone cells, bone tissue, fracture, non-union, prosthesis and vertebral fracture; and (3) chondrocyte, synoviocytes, joint chondroprotection, arthroscopy and knee arthroplasty.

RESULTS

Pre-clinical studies have shown that the site of interaction of biophysical stimuli is the cell membrane. Its effect on bone tissue is to increase proliferation, synthesis and release of growth factors. On articular cells, it creates a strong A_2A and A₃ adenosine-agonist effect inducing an anti-inflammatory and chondroprotective result. In treated animals, it has been shown that the mineralisation rate of newly formed bone is almost doubled, the progression of the osteoarthritic cartilage degeneration is inhibited and quality of cartilage is preserved. Biophysical stimulation has been used in the clinical setting to promote the healing of fractures and non-unions. It has been successfully used on joint pathologies for its beneficial effect on improving function in early OA and after knee surgery to limit the inflammation of periarticular tissues.

DISCUSSION

The pooled result of the studies in this review revealed the efficacy of biophysical stimulation for bone healing and joint chondroprotection based on proven methodological quality.

CONCLUSION

The orthopaedic community has played a central role in the development and understanding of the importance of the physical stimuli. Biophysical stimulation requires care and precision in use if it is to ensure the success expected of it by physicians and patients.

Effects of pulsed electromagnetic stimulation on patients undergoing hip revision prostheses: a randomized prospective double-blind study

In this prospective, randomized, double-blind study, the effect of Pulsed Electromagnetic Fields (PEMFs) was investigated in 30 subjects undergoing hip revision using the Wagner SL stem. The subjects were treated for 6 h/day up to 90 days after revision. Study end points were assessed clinically by the functional scale of Merle D'Aubigné and instrumentally by Dual-Energy X-ray Absorptiometry (DXA) at the Gruen zones. Subject improvement according to Merle D'Aubigné scale was higher (P < 0.05) in subjects undergoing active stimulation compared to placebo. In analyzing the DXA findings, we subtracted for each area the postoperative bone mineral density (BMD) values from those measured at 90 days and we considered all results above 3.5% as responders. There were no significant differences in the average BMD values at each Gruen zone between the two groups both postoperatively and at 90 days investigation. In Gruen zones 5 and 6, corresponding to the medial cortex, we observed six responders (40%) in both areas in the control group, while in the stimulated group we observed 14 (93%) and 10 (66%) responders, respectively (both P < 0.05). This study showed that PEMF treatment aids clinical recovery and bone stock restoration.

Current trends in the enhancement of biomaterial osteointegration: biophysical stimulation

To enhance bone implant osteointegration, many strategies for improving biomaterial properties have been developed which include optimization of implant material, implant design, surface morphology and osteogenetic coatings. Other methods that have been attempted to enhance endogenous bone healing around biomaterials are different forms of biophysical stimulations such as pulsed electromagnetic fields (PEMFs) and low intensity pulsed ultrasounds (LIPUS), which were initially developed to accelerate fracture healing. To aid in the use of adjuvant biophysical therapies in the management of bone-implant osteointegration, the present authors reviewed experimental and clinical studies published in the literature over the last 20 years on the combined use of biomaterials and PEMFs or LIPUS, and summarized the methodology, and the possible mechanism of action and effectiveness of the different biophysical stimulations for the enhancement of bone healing processes around bone implanted biomaterials.

Enhancement of bone formation by drawn poly(L-lactide)

Poly(L-lactide) (PLLA) was molded into films and rods, and drawn in the longitudinal direction to endow them with piezoelectricity. The piezoelectric constants of PLLA films increased with the draw ratio and, after passing a maximum at a draw ratio around 5, decreased. PLLA samples with a draw ratio 5 underwent fibrilization. The PLLA rods were intramedullarily implanted in the cut tibiae of cats for internal fixation up to 8 weeks. Fracture healing was clearly promoted with increased callus formation as the draw ratio of the PLLA rod increased, whereas the undrawn PLLA as well as a polyethylene control rod had no effect on callus formation, or rather, retarded it. This finding strongly suggests that the promotion of fracture healing by fixation with drawn PLLA can be ascribed to the piezoelectric current generated by the strains accompanying leg movement.