Anthony L.B. Rhodes

Wavelength selection in laser arthroscopy

Electrosurgical devices and various lasers are used to cut human meniscal tissue, and the amount of thermal damage caused by each method is measured and compared.

Carbon dioxide laser removal of polymethylmethacrylate.

Polymethylmethacrylate remains an excellent method of securing orthopaedic implants. However, revision surgery may be necessary when loosening of the prosthesis has occurred with symptomatology. Removal of polymethylmethacrylate during revision surgery can be difficult. Care must be taken to avoid damage to the remaining bone and surrounding soft tissue. This study was undertaken to characterize the efficacy of the carbon dioxide (CO2) laser for cement removal in vitro and in vivo. The CO2 laser did not damage adjacent bone or soft tissue via lateral heat transfer in vitro and in vivo. The maximum bone cortex temperature during CO2 laser removal was 56 degrees C. This was lower than the 60 degrees C temperature encountered during initial cement insertion and curing. The CO2 laser preferentially penetrates polymethylmethacrylate with absorption versus apparent relative reflection with bone. The products of vaporization from CO2 laser removal of polymethylmethacrylate were removed safely (to < 12.2 ppm) with a smoke evacuator without risk to the patient or operating room personnel. Removal of polymethylmethacrylate by CO2 laser was performed in 117 patients undergoing revision operations, including 78 total hip revisions, 33 total knee revisions, 3 total elbow revisions, and 3 spine revisions. No perforation or fracture of bone occurred with the use of the laser. There was no statistical difference in surgical time, blood loss, infection rate, or hospital stay when the CO2 laser was used. There were no cases of osteonecrosis or obvious soft tissue necrosis caused by the laser. The infection rate was 3.4% (4/117) when the laser was used for cement removal.

Lasers in orthopedics

Orthopedic Surgery is that surgical discipline which deals with the musculoskeletal system. Orthopedists therefore operate on joints, the spine and long bones and engage in such subsecialities as sports medicine, hand surgery, trauma surgery, and joint replacements. Since they must cut and shape bone, cartilage, tendon, and ligament, orthopedists have developed a number of mechanical techniques to achieve these ends and surgical lasers have found few applications in orthopedics because until now they have not been useful for cutting bone. In the past several years, however, there has been considerable interest in several areas within the field of orthopedic surgery that do not entail actual bone surgery and it is expected that as newer and more powerful lasers become available laser osteotomy may become feasible and even routine.

Nd:YAG 1.44 laser ablation of human cartilage

This study determined the effectiveness of a Neodymium:YAG 1.44 micrometers wavelength laser on human cartilage. This wavelength is strongly absorbed by water. Cadaveric meniscal fibrocartilage and articular hyaline cartilage were harvested and placed in normal saline during the study. A 600 micrometers quartz fiber was applied perpendicularly to the tissues with a force of 0.098 N. Quantitative measurements were then made of the ablation rate as a function of fluence. The laser energy was delivered at a constant repetition rate of 5 Hz., 650 microsecond(s) pulsewidth, and energy levels ranging from 0.5 joules to 2.0 joules. Following the ablation of the tissue, the specimens were fixed in formalin for histologic evaluation. The results of the study indicate that the ablation rate is 0.03 mm/mj/mm2 for hyaline cartilage and fibrocartilage. Fibrocartilage was cut at approximately the same rate as hyaline cartilage. There was a threshold fluence projected to be 987 mj/mm2 for hyaline cartilage and fibrocartilage. Our results indicate that the pulsed Nd:YAG laser operating at 1.44 micrometers has a threshold fluence above which it will ablate human cartilage, and that its ablation rate is directly proportional to fluence over the range of parameters tested. Fibrocartilage and hyaline cartilage demonstrated similar threshold fluence and ablation rates which is related to the high water content of these tissues.

High Resolution Analysis of Ground Foot Reaction Forces

A new system of hardware and software has been designed for quantitative high resolution analysis of ground foot pressures during stance and gait. In the system, a large photoelastic sheet is used as the transducer and a computerized video system for analysis and display. This system offers a larger active surface at higher resolution and at lower cost than any other system heretofore described. It will be used to predict diabetic plantar ulceration as well as to detect anatomic and motor defects affecting the feet.

Percutaneous lumbar discectomy using Ho:YAG laser

The Ho:YAG laser is used to perform percutaneous lumbar discectomy in swine to evaluate the procedure as a potential clinical tool.

Technique of CO2 laser arthroscopic surgery

The CO2 laser was selected for arthroscopic surgery due to its availability in the hospital high power output and excellent absorption by unpigmented tissues. During the course of this study 4 generations of laser instruments were tested. These include the focused beam delivered via a handpiece the (3 mm O.D.) macrowaveguide the (1.5 mm Q.D.) microwaveguide and the flexible waveguide. The latter two devices complement each other in that the microwaveguide will tolerate and retain up to a 30 degree(s) curve. The flexible waveguide will clear narrow joint tolerances without creating lesions in the articular surface. CO2 laser arthroscopic tissue ablation must be done under gaseous joint distention but this presents no undue difficulties. At the completion of the procedure saline irrigation must be done for char removal.

Stimulatory effects of Nd:YAG lasers on canine articular cartilage

PURPOSE: To determine the effects of Nd:YAG laser energy on the healing of full- and partial-thickness articular cartilage defects in canines

308-nm excimer laser ablation of human cartilage

The XeCl excimer laser was investigated as an ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800 micrometers fiber with the laser delivering a range of fluences (40 to 190 mj/mm2) firing at a frequency of 5 Hz. To assess the effect of repetition rate on ablation rate, a set of measurements was made at a constant fluence of 60 mj/mm2, with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage at the maximum fluence tested. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10 - 70 micrometers ).

CO2 partial matricectomy in the treatment of ingrown toenails

Conventional treatment of ingrown toenails requires ablation of the nail bed by curettage with or without the use of cauterizing agents such as phenol. Despite these measures, incomplete ablation of the ingrown nail does occur, often requiring additional procedures. This recurrence rate is reported to as high as 50% in some series. The purpose of this study is to see if CO2 partial matricectomies were more effective in treating symptomatic ingrown toenails. In particular, the authors looked at the recurrence rate and infection rate.