Introduction

Arthroscopy can be a useful tool when treating dogs for cranial cruciate ligament rupture. Arthroscopic-assisted debridement of the torn ligament and treatment of meniscal tears prevents the need for arthrotomy and incision of other periarticular soft tissues. Meniscal release can also be performed under arthroscopic guidance. Lower morbidity and enhanced visualization is achieved with arthroscopy. Second-look arthroscopic evaluation of patients undergoing previous stabilization for cruciate tears is indicated for treatment of meniscal tears, meniscal release, and evaluation of the cranial cruciate ligament, caudal cruciate ligament, previous meniscal procedures, osteoarthritis and synovitis. Patterns of articular wear can be assessed in patients having an unsatisfactory outcome following TPLO. Second-look arthroscopy is particularly valuable for low morbidity follow-up evaluations of the joint in experimental studies.

Arthroscopic Changes

First look arthroscopic evaluation in patients having cruciate ligament disease often have substantial synovitis that may obscure visualization. Synovitis has usually subsided at the time of second-look arthroscopy. Villous hypertrophy present at the time of an acute ligament tear subsides at follow-up examination in patients having a favorable outcome following TPLO.

Torn fibers associated with partial tears of the cranial cruciate ligament can be debrided at the initial arthroscopic exam. Evaluation of the ligament during second-look generally reveals a healthy appearance characterized by reduced hyperemia, no additional fiber tearing and grossly normal tensile properties. The improved appearance of the cranial cruciate ligament at second-look arthroscopic examination supports the theory that TPLO reduces strain on the cranial cruciate ligament.

The caudal cruciate ligament appears normal in most dogs at the time of second-look arthroscopy, despite the probable development of caudal tibial thrust following TPLO. The caudal cruciate ligament frequently has mild fraying or tearing of fibers at the time of initial arthroscopic examination in dogs having cranial cruciate ligament disease. These fibers can be debrided carefully with a radiofrequency probe at the time of TPLO and usually appear normal at the time of second-look arthroscopy.

Meniscal changes are occasionally found at second-look arthroscopic exam. Typically these changes are minor and include mild fraying of the free edge of the medial or lateral meniscus. These tears are classified as radial tears. Small tears can be meticulously debrided with a radiofrequency probe, being careful to avoid the articular cartilage. When using the radiofrequency probe for meniscal debridement, the probe should be applied in short bursts and lavaged continuously with ample fluids to reduce the chance of iatrogenic damage to adjacent cartilage. Other meniscal changes that have been seen at second-look arthroscopy include bucket-handle tears, meniscal degeneration and calcification. Menisci typically appear healthy at second-look arthroscopic exam if previously treated by partial meniscectomy at the time of TPLO. Medial meniscal release performed at the meniscotibial ligament appears to remain functional and show no evidence of healing at the time of second-look arthroscopy. Midbody meniscal release performed caudal to the medial collateral ligament also appears to remain functional, but some healing may occur and is grossly characterized by fibrous tissue spanning the meniscal gap. In these cases, the meniscus appears to be elongated with respect to its original length before meniscal release.

Arthroscopic evaluation was recently performed in 16 dogs (22 stifles) having a partial tear of the CrCL and TPLO as part of an ongoing clinical study. A meniscal release incision was performed in 4 stifles. A second-look arthroscopic evaluation was performed 3 to 33 months after TPLO (mean 10.4 months). Arthroscopic evaluation of the cranial and caudal cruciate ligaments, lateral and medial menisci, femoral and tibial cartilage, periarticular osteophyte (PAO) formation and degree of synovitis was performed. Pathologic changes were identified at initial surgery and followed over time.

Radiographic evidence of PAOs was unchanged or minimally increased in 20 stifles and moderately increased in 2 stifles. Progression of PAOs was evident arthroscopically in 36% of stifles. Cartilage wear was unchanged in 12 stifles and increased in 10 stifles. Cartilage wear was evident arthroscopically in 7 stifles without radiographic evidence of increased osteoarthritis. Small radial tears of the lateral meniscus were seen in 19 stifles at the time of initial surgery. Six of 8 stifles treated by radiofrequency partial meniscectomy had increased cartilage wear. Increased cartilage wear was evident in 2 of 11 stifles with similar meniscal tears left untreated. The severity of synovitis was unchanged in 2 and decreased in 20 stifles. The CrCL was intact at follow-up in 19 of 22 stifles. The caudal cruciate ligament (CdCL) was normal in 18 of 22 stifles at time of TPLO. Four dogs had obvious fraying of the CdCL at initial surgery. The CdCL was frayed in 10 of 22 stifles at second-look arthroscopy. The meniscal release incision was not healed in 2 of 4 stifles and was spanned with a fibrous tissue in 2 of 4 stifles.

Arthroscopy was a more sensitive indicator of increased PAO formation following TPLO. Synovitis was generally decreased at follow-up. The intact portion of the CrCL had a high chance of remaining intact following TPLO. Increased fraying of the CdCL may be due to the increased load following TPLO. Meniscal release incisions did not heal or healed with fibrous tissue. Small radial tears of the lateral meniscus may not require treatment. TPLO does not eliminate osteoarthritis in dogs having partial tears of the CrCL, but does appear to avoid complete rupture.

Complications

Complications are infrequent following second-look arthroscopy. The procedure is usually much shorter in duration, often times completed in less than 15 minutes. The predominant complication is subcutaneous fluid extravasation. Infection is rare if aseptic technique is used. Morbidity is extremely low- patients rarely have lameness induced by the procedure.

	A partial tear of the cranial cruciate ligament was treated in this Rottweiler, 6 months previously. The ligament appears healthy at 2nd look arthroscopic exam.
	A mid-body meniscal release is seen to be intact and functional when observed 1 year postoperatively.
	Small radial meniscal tears were seen at 2nd look arthroscopic exam of this TPLO patient.
	The radial tears were ablated using a radiofrequency probe.
	Menisci can be critically evaluated at 2nd look arthroscopic exam. This meniscus is normal in a TPLO patient 2 years after surgery.
	Occasionally fraying of PCL fiber will be seen at 2nd look arthroscopic exam in TPLO patients.