Osteonecrosis of the knee following laser-assisted arthroscopic surgery: A report of six cases

Case Report

Osteonecrosis of the Knee Following Laser-Assisted Arthroscopic Surgery: A Report of Six Cases

Jonathan P. Garino, M.D., Paul A. Lotke, M.D., Alex A. Sapega, M.D., Philip J. Reilly, M.D., and John L. Esterhai, Jr., M.D.

Summary: We report six cases where significant postoperative pain persisted in individuals following arthroscopic surgery augmented with the use of lasers. Subsequent magnetic resonance images showed lesions with signal changes com- patible with the diagnosis of osteonecrosis in areas directly addressed with laser energy. Key Words: Laser-Osteonecrosis-Complication-Arthroscopy.

T he surgical application of laser energy in orthopae- dies is gaining popularity. There are many clinical

reports in the recent literature regarding the utility and efficacy of adjunctive laser intervention during arthroscopy.‘-* A variety of problems about the knee involving articular cartilage, menisci, and synovium are felt to be amenable to laser treatment. Research examining the extent of the zones of thermal energy spread has been done for most types of laser energy on articular cartilage and menisci, and thought not to be significant in most clinical settings.425,7~s~‘0-13 Although thermal damage is discussed or mentioned by most investiga- tors as a possible complication, significant thermal damage to adjacent structures has not been a reported complication in any clinical series up to the present~4,5,7,8,10-‘3 We report on five patients (six knees) with para-articular osteonecrosis following arthroscopic knee surgery in which a laser was used to assist in the treatment of articular cartilage and meniscal pathology. To our knowledge, this complication following an

From the Department of Orthopaedic Surgery, University of Penn- sylvania School of Medicine, Philadelphia, Pennsylvania, U.S.A.

Address correspondence and reprint requests to Jonathan P. Ga- rino, M.D., Dep&nent of Orthobaedic Surgery, the University of Pennsylvania School of Medicine, 3400 Suruce St, Philadeluhia, PA 19104: U.S.A. ”

0 1995 by the Arthroscopy Association of North America 0749-8063/95/l 104-1279$3.00/O

arthroscopic procedure using laser energy has not been reported.

CASE 1

J. M. is a 44-year-old woman who injured her right knee during a fall. She presented with complaints of medial knee pain. Initial radiographs were interpreted as normal. A magnetic resonance image (MRI) was obtained that showed degenerative signal in the medial meniscus, with unremarkable articular and osseous anatomy. At 4 months after her injury, the patient remained symptomatic and underwent arthroscopic knee surgery utilizing a contact Neodymium:Yttrium-Alu- minum-Garnet (Nd:YAG) laser in a saline fluid me- dium. A tourniquet was not used during surgery. Arthroscopy reportedly revealed a small radial tear of the posterior horn of the medial meniscus and a 1.5 cm diameter area of grade IV articular cartilage degen- eration on the posterior, weight-bearing surface of the medial femoral condyle. A minimal, inner edge partial meniscectomy using laser technique was accom- plished, and degenerated articular cartilage on the medial condyle was debrided mechanically. The laser probe was then reportedly used to ‘ ‘carmelize” the remaining abnormal articular cartilage on the femur. The total laser energy delivered during the procedure was recorded as 54,133 J. No specific energy amounts

Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 11, No 4 (August), 1995: pp 467-474 467

468 J. P. GARINO ET AL.

FIG 1. MRI of right knee 8 months following initial arthroscopic procedure. (A) Transverse section, (B) coronal, (C) sagittal. Note different signal characteristics of femoral and tibia1 lesions, and circum- ferential configuration of femoral lesion on transverse section.

to each of the various areas addressed with the laser were recorded.

Although never asymptomatic, the patient slowly improved for 8 months following arthroscopy. She then suddenly developed severe medial knee pain and swelling. Repeat radiographs faintly suggested a geographic lesion of the medial femoral condyle. A bone

scan showed intense technetium pyrophosphate uptake in the medial hemi-joint. At 9 months postoperatively, a repeat MRI (Fig 1) showed two geographic osseous lesions, one in the medial femoral condyle and the other in the tibia1 plateau, consistent with osteonecrosis. The patient’s medical history was unremarkable, without evidence of alcohol or steroid use.

OSTEONECROSIS FOLLOWING LASER ARTHROSCOPY 469

FIG 2. Arthroscopic view of medial femoral condyle in area directly overlying lesion seen on MRI. Note blackened indentation marks on exposed femoral cortex.

Ten months after the initial procedure, repeat arthroscopy showed a 2 X 2.5 cm, grade IV articular cartilage defect of the medial femoral condyle with multiple, small, blackened recesses on the exposed femoral cortex that had the gross appearance of char marks (Fig 2). The cortex was otherwise intact. The edges of articular cartilage at the perimeter of the lesion were unstable and peeling. The location of this articular lesion was directly over the region of femoral osteonecrosis seen by MRI. The medial tibia1 plateau had a circular area of fissuring and fibrillation in the adjacent anterior weight-bearing region but no charring or gross evidence of laser debridement. Arthroscopic core decompression, percutaneous drilling, and biopsy examination of the medial condylar lesion were performed, followed by local autogenous cancellous bone grafting of the femoral core defect. Percutaneous nee- dle biopsy (two small cores) of the tibia1 lesion was then performed using radiographic guidance. Intraop- erative cultures were negative. Histological evaluation of all specimens showed osteonecrosis (Fig 3). The only viable bone was found at the deep end of the femoral core, which had passed completely through the zone of necrotic bone. Signs of creeping substitu- tion were seen at the transition interface between live and dead bone.

One year following the second arthroscopic procedure, the patient remained symptomatic and underwent unicompartmental knee replacement with good early result (Figs 4 and 5).

CASE 2

S. A. is a 44-year-old printer who sustained a twist- ing injury to his left knee. Initial radiographs were negative except for mild medial compartment degener- ation. An MRI performed 1 week later showed a torn medial meniscus. All bone structures and the lateral meniscus were normal. Eleven days later, the patient had left knee arthroscopy with a partial resection of the posterior aspect of the medial meniscus. Grade II chondromalacia was found at the undersurface of the patella, medial tibia1 plateau, and lateral tibia1 plateau. A laser chondroplasty of these areas was then performed using a Nd:YAG laser at 60 W. Postopera- tively, the patient continued to have significant knee pain, most of which was lateral. Ten weeks following surgery, a repeat MRI was performed (Fig 6A). Signal changes consistent with osteonecrosis in a moderate sized area of the lateral tibia1 plateau and a small area of the lateral femoral condyle were seen. Observation and symptomatic treatment was rendered, and the patient slowly improved. A third MRI was performed 6 ’ months after the initial procedure, and it revealed z nearly complete healing of the defects (Fig 6B). The patient is currently back at work on light duty with some residual symptoms, but they are mostly medial.

CASE 3

J. C. is a 30-year-old woman with a possible history of juvenile rheumatoid arthritis who had many years

FIG 3. Section of femoral core biopsy specimen showing avascular bone. (H&E stain, original magnification X100).


FIG 4. Anterior-posterior and lateral radiographs taken just be- fore unicompartmental replacement. Note lesions in femoral condyle and tibia1 plateau.

of worsening right knee pain. Radiographs of the right knee showed mild osteopenia of all bone about the knee and mild arthritic changes in the medial and patella femoral compartments. The patient underwent right knee arthroscopy and low energy laser chondroplasty of the patella and medial femoral condyle with a Nd:YAG laser. Postoperatively, her knee pain was unimproved, and actually had increased. Conser- vative symptomatic care was employed, but her knee pain worsened. An MRI was performed 7 months after laser arthroscopy. Large areas of abnormal signal consistent with osteonecrosis were observed in the medial femoral condyle and the majority of the patella (Fig 7). Repeat arthroscopy was performed 1 week later. Mild general discoloration of the articular surfaces was noted. A small, 5 X 10 mm, area of loose cartilage on

the medial femoral condyle was debrided. Multiple drill holes were placed into the anterior surface of the patella in an effort to decompress and heal the patella lesion. Pathological examination of these patellar biopsy specimens showed necrotic bone. One year following this procedure, the patient had a patellectomy with resolution of the majority of her pain. The histol- ogy of the resected patella confirmed osteonecrosis of nearly the entire patella. There was no articular cartilage remaining on the chondral surface.

CASE 4 AND 5

K. L. is a 30-year-old woman with a long history of bilateral chondromalacia patellae. She developed a sudden exacerbation of her baseline discomfort that

FIG 5. Anterior-por diogr ,aph: s following pan lent replacement.

3terior unicl

ra- om-


FIG 6. MRI of knee at (A) 10 weeks and (B) 6; months after laser-assisted arthroscopy. Note improvement of lesions in the medial femoral condyle and tibia1 plateau over the 4-month period.

did not respond to conservative treatment modalities including physical therapy and anti-inflammatory agents. A maltracking problem was suspected, and an arthroscopic lateral release was performed on both knees. The patient had little clinical improvement, and resumed conservative care. After 1 year with essentially no change in her symptoms, a bilateral laser assisted patellar chondroplasty was performed with the Nd:YAG laser. The patient had significantly more pain following this procedure for nearly 9 months, at which time an MRI was performed. Large areas of decreased signal intensity were present in both patellae (Fig 8) consistent with osteonecrosis. Her pain and disability at this time is of sufficient magnitude that patellectomy is currently under consideration.

FIG 7. MRI showing extensive (A) patellar osteonecrosis and (B) significant reciprocal lesion on anterior femur.


FIG 8. MRI showing large areas of decreased signal intensity within the (A) right and (B) left patellae, consistent with osteonecrosis.

CASE 6

C. W. is a 50-year-old woman who had significant left knee pain after a fall. She had pain, catching, pop- ping, and buckling involving the lateral side of the knee. After 2 months of unsuccessful conservative care, she underwent arthroscopy for suspected lateral men&al tear. At arthroscopy, a partial thickness chondral fracture was found. A laser chondroplasty of the lateral femoral condyle was then performed using a Hol:YAG laser. The patient did not significantly im- prove, and 6 months later she had an MRI to evaluate her knee. A large, well-circumscribed lesion of the lateral femoral condyle consistent with osteonecrosis (Fig 9) was shown. The patient is currently being treated symptomatically.

DISCUSSION

These six cases together show strong circumstantial evidence suggesting that serious injuries to the adjacent bony structures can occur following laser assisted arthroscopic procedures. Although several types of lasers with a variety of delivery systems are currently

available, a contact Neodinium:YAG laser appears to have been used in five of these cases whereas Hol:YAG apparently was used in one. All areas of abnormal signal in all cases were located either directly below or adjacent to regions of articular cartilage or meniscal tissue addressed with laser energy. All cases have oper- ative note documentation of laser usage in the areas that have subsequently shown changes on MRI.

The Nd:YAG laser emits light energy at a wavelength of 1.06 pm. At this wavelength, the emitted energy is poorly absorbed by water and nonpigmented tissues (e.g., meniscal tissue and hyaline cartilage).53739 As such, a free beam of this type is poorly suited for most orthopaedic applications. Consequently, a ce- ramic or sapphire contact probe placed on the tip of the fiberoptic wand was added. This contact probe theoretically provides a system by which laser energy can be precisely delivered to the intended tissues as well as a mode for tactile feedback.5’g However, with this situation, the bulk of the laser energy delivered to the probe is converted into heat. Thus, the tip of the laser functions as a contact thermal device.5,7’g The Hol- mium:YAG laser emits light energy at a wavelength of 2.1 pm which is highly absorbed by cartilage and


FIG 9. (A) Sagittal and (B) coronal MRI cuts showing large, well- circumscribed lesion within the lateral femoral condyle consistent with osteonecrosis.

meniscal tissue. The laser light is fiberoptically delivered in microsecond pulses with a range of energies.14 This theoretically delivers less energy to the underlying bone.

We believe these cases may show a serious potential complication of performing intra-articular procedures using a lasers, particularly Nd:YAG. Although an MRI may reflect juxta-articular bone and soft tissue changes

following a routine arthroscopy with mechanical debridement of meniscus and cartilage, we feel that these dramatic postoperative changes in areas addressed with a laser in different patients by different surgeons are highly suspicious for laser-induced osteonecrosis. Ex- periments on articular cartilage have shown the laser’s effects to be extremely dose dependent with total energies of as little as 125 J (25-W pulses) to localized areas resulting in subchondral bone damage.15 Other animal studies have shown injury and osteonecrosis to subchondral bone treated with both Nd:YAG and Holmium:YAG lasers.16“8

There are several possible causes of laser-induced osteonecrosis. Bone death may have resulted directly from excessively high temperatures; indirectly because of pressure/inflammatory changes secondary to injury to the subchondral plate in a manner similar to osteo- chondritis dessicans; or from a photoacoustic insult. The concept of a pure thermal cause is weakened by the fact that thermal destruction of underlying bone is graduated with blood flow in the area assisting in the dissipation of heat, and that high temperatures exist only within a few millimeters of the probe.‘,” As such, large areas resulting from thermal necrosis would be less likely.

A possible and still poorly understood mechanism for the development of such large lesions is photoacoustic shock. When water or other cell constituents are changed from solid or liquid phase to a gas or vapor in just a few milliseconds at the tip of the laser probe, there is a sudden and rapid expansion these newly created gases.14%18 This may be more common or more injurious with the use of contact tip types of laser probes. With the laser probe essentially pressed up against the cartilage, an acoustic shock wave is directed into the surrounding bone. If an area is addressed with the laser for 10 minutes at 2 Hz, that would represent 1,200 photoacoustic insults to the surrounding bone, which is an excellent conductor of sound. This concept is in some ways similar to the shock wave that passes through the liver as a high- velocity missile penetrates this organ, causing cell death at a significant distance from the actual path of the projectile.

Lasers are becoming increasingly popular in orthopaedics. The technical nature and minimalist approach to intra-articular pathology have made lasers an im- portant potential adjunct to arthroscopic knee surgery. The ability to deliver laser energy precisely to the areas of pathology is appealing, but this preciseness may also concentrate the energy, creating the potential for a significant injury for a patient.

J. P. GARINO ET AL.

We have observed six cases of osteonecrosis possi- bly resulting from laser chondroplasty. Because this complication can have a serious effect on the joint, we recommend that prospective studies on the safety and efficacy of laser chondroplasty be performed and reported. In addition, the orthopaedists choosing to use a surgical laser should have a sound fundamental grasp of the biophysics of lasers as well as an awareness of the potential for injury to the joint.

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Osteonecrosis of the knee following laser-assisted arthroscopic surgery: A report of six cases