Development of a virtual reality arthroscopic knee simulator.

The virtual reality arthroscopic knee simulator (VR-AKS) consists of a computer platform, a video display, and two force-feedback (haptic) interfaces which also monitor the position of the instruments in the user's hands. The forces that the user would normally apply to the lower limb during arthroscopy are directed through an instrumented surrogate leg. Proprietary software furnishes the mathematical representation of the physical world and replicates the visual, mechanical, and behavioral aspects of the knee while task-oriented programs monitor and record specific areas of user performance. A prototype has demonstrated the feasibility of the system and work on the first, fully functional simulator will begin soon.

Return of motion after simultaneous repair of displaced bucket-handle meniscal tears and anterior cruciate ligament reconstruction.

Patients with displaced bucket-handle (DBH) meniscal tears in anterior cruciate ligament (ACL)-deficient knees are prone to flexion contracture following meniscal repair and simultaneous ACL reconstruction. It has been suggested that ACL reconstruction be delayed until full range of motion has returned after the meniscal repair. A retrospective analysis was performed comparing the return of extension in patients undergoing simultaneous ACL reconstruction and repair of DBH tears (group A) versus a control group of patients with non-DBH tears (group B). Age, sex, body mass index, duration of time from injury to surgery, and preoperative extension were also compared between groups and evaluated for their significance as risk factors. Patients in group A achieved recovery to -5 degrees and 0 degrees of extension 22% and 35% more slowly, respectively, when compared with group B. These differences were not statistically significant. Female patients tended to heal more rapidly in both groups. We conclude that a one-stage procedure is sufficient in allowing patients with DBH tears in ACL-deficient knees to regain a functional knee to within 5 degrees of full extension.

Arthrometric evaluation of posterior cruciate ligament injuries.

We reviewed the clinical examinations and knee arthrometry evaluations of 40 patients: 10 with posterior cruciate ligament injuries, 10 with combination anterior and posterior cruciate ligament injuries, 10 with anterior cruciate ligament injuries alone, and 10 with no history of knee injury. Using a 3-mm side-to-side difference as the minimal limit for detection of posterior cruciate ligament injury, the sensitivity of the arthrometer at 40 pounds of posterior force was 90%, the specificity was 100%, the predictive value of a positive test was 100%, and the predictive value of a negative test was 91%. When total anterior-posterior translation was assessed, the sensitivity was 100%, the specificity was 85%, the predictive value of a positive test was 87%, and the predictive value of a negative test was 100%. The overall accuracy of arthrometry for detection of posterior cruciate ligament injury was 96% for 40 pounds of posterior force and 94% for total anterior-posterior translation at 40 pounds. Grade 1 posterior cruciate ligament injuries had significantly greater arthrometric posterior translation compared with grade 0 (normal) knees. Regression analysis showed arthrometric laxity measurements correlated well with the clinical grade of the posterior drawer test. Finally, the accuracy of the arthrometer was not affected by concomitant anterior cruciate ligament injury.

The absent bow tie sign in bucket-handle tears of the menisci in the knee.

OBJECTIVE: Bucket-handle tears of the menisci are one of the most frequently missed diagnoses in MR examinations of the knee. This article describes the "absent bow tie sign," which can be used to identify bucket-handle tears on routine MR examinations of the knee. MATERIALS AND METHODS: The arthroscopic surgical reports (n = 350) from a single orthopedic surgeon's practice during a 24-month period were examined for patients who had a diagnosis of bucket-handle tear and who underwent MR imaging before surgery (n = 32). The MR examinations were retrospectively evaluated for the presence of a bow tie sign. The bow tie sign was considered normal when two sagittal images showed the body segment (a bow tie appearance). The bow tie sign was considered abnormal, consistent with a bucket-handle tear, when only one or no body segment was seen (the absent bow tie sign). Coronal images were evaluated for a truncated meniscus. Also, each MR examination was scrutinized for a displaced fragment and a double posterior cruciate ligament (PCL) sign. RESULTS: Thirty-three bucket-handle tears were found at arthroscopy in 32 patients. One patient had tears of the medial and lateral menisci. The absent bow tie sign was seen in 32 of the 33 cases (sensitivity, 97%) and correlated with the medial or lateral meniscus that was reported torn at arthroscopy. The single false-negative result occurred in a patient with a nondisplaced bucket-handle tear. The findings in 31 contralateral normal menisci were all negative for an absent bow tie sign (specificity, 100%). A displaced fragment was found in 30 (94%) of 32 cases. The coronal images showed a truncated meniscus in 21 (64%) of 33 cases. A double PCL sign was seen in 10 (30%) of 33 cases. CONCLUSION: The absent bow tie sign is an easily applied finding that can be used with good sensitivity to diagnose bucket-handle tears of the menisci on MR imaging. This sign has a higher accuracy rate than other findings common with bucket-handle tears, such as displaced fragments, a truncated appearance of the meniscus on coronal images, and the double PCL sign.

Osteonecrosis after contact neodymium:yttrium aluminum garnet arthroscopic laser meniscectomy.

OBJECTIVE: The purpose of this report is to describe two cases of osteonecrosis that occurred after arthroscopic meniscectomy with a contact neodymium:yttrium aluminum garnet laser system. The patients developed increasing knee pain and disability 5 months and 6 months after laser meniscectomy. MR imaging showed subchondral osteonecrosis in the femoral condyle and tibial plateau immediately adjacent to the site of laser meniscectomy in both patients. One patient required a total knee replacement to alleviate knee symptoms, and the other patient required a tibial osteotomy and surgical elevation of collapsed tibial articular surface. CONCLUSION: To our knowledge, this complication of laser arthroscopic meniscectomy has not been reported in the radiology literature. The clinical and MR imaging features of this important complication are described and possible causative mechanisms are discussed.

Elongation of arthroscopically tied knots.

It has been postulated that some arthroscopic shoulder stabilization failures may be due to knot slippage. In an effort to improve arthroscopic technique, we performed tensile testing on four arthroscopically tied knots with two commonly used suture materials. Handtied square knots served as controls. Sutures of No. 1 Maxon and No. 1 Ticron were used. Four types of sliding knot configurations were tested: the overhand loop, the Duncan loop, the Roeder knot, and the Snyder knot. Knots were tied via a knot pusher, and testing was performed in a normal saline-filled thermoplastic chamber. Knots were tied around two rings connected to a Bionix 858 materials testing apparatus. The knots were tested under conditions of cyclic loading and loading to failure. Results of the testing revealed that the most important factor in knot security was the type of suture material, although there were differences with the type of knot. With the Maxon suture, there was significantly decreased ultimate failure load of all of the arthroscopically tied knots compared with handtied square knots. Knots tied with Ticron were similar in strength for both arthroscopically and handtied groups. The surgeon who chooses a monofilament absorbable suture should be aware that a high percentage of knots fail under low load cyclic testing, and that all of these knots were inferior to handtied square knot controls in testing to failure.

Effect of reconstruction of the anterior cruciate ligament on proprioception of the knee and the heel strike transient.

Abnormal proprioception of the knee joint has been documented after rupture of the anterior cruciate ligament (ACL) and may result in the loss of muscular reflexes. Excessive loading from the lack of muscular control may predispose the joint to osteoarthrosis. To investigate this problem, 10 patients were studied at an average of 31.6 months after ACL reconstruction. Three tests of joint proprioception and measurements of the vertical component of heel strike force during normal gait were used. A normal control group also was studied. For two of the proprioception tests (reproduction of passive motion and relative reproduction), there were no statistical differences among the uninjured (control) limbs, the normal contralateral limb of patients with a reconstructed ACL, and the extremity with a reconstructed ACL. In the third test (threshold of detection of motion), which previously has been shown to be adversely affected by ACL injury, the measurements for both extremities of patients with a reconstructed ACL were more accurate than those for the control group. The reconstructed extremity performed less accurately than the contralateral extremity (p < 0.05). The heel strike transient (vertical component of ground reaction force at heel strike) for uninjured and ACL-reconstructed limbs was not significantly different. In fact, the extremity with the reconstructed ACL had a lower transient than the uninjured extremity. Heel strike transients in patients with a reconstructed ACL were higher than those in the controls, but the differences were significant only when corrected for velocity of gait.(ABSTRACT TRUNCATED AT 250 WORDS)

The incidence of healing in arthroscopic meniscal repairs in anterior cruciate ligament-reconstructed knees versus stable knees.

In this study, follow-up data was obtained in 90 of 117 consecutive meniscal repairs. In Group I, there were 68 meniscal repairs in conjunction with anterior cruciate ligament reconstruction, and in Group II, 22 isolated repairs in anterior cruciate ligament stable knees. Meniscal healing was assessed using the criteria established by Henning, by either arthroscopy or arthrography, at a mean of 7 months for isolated repairs and a mean of 10 months for repairs done in conjunction with anterior cruciate ligament reconstruction. Average time from injury to surgery was 19 months in Group I patients, and 14 months in Group II patients. The overall rate of successful healing was 82%. Group I repairs were successful 93% of the time compared to a 50% success rate in Group II (P less than 0.00005). Lateral meniscal repairs fared better than medial repairs in both groups. Although a smaller rim width yielded better overall healing, there was no difference in the mean rim width of the two groups. Patients with anterior cruciate ligament reconstruction did better than those with isolated meniscal repair, regardless of tear length. Older patients had better healing than younger ones. Overall, acute repairs were more successful than repairs of chronic tears. Even so, the chronic Group I patients had a 91% successful healing rate.

AIDS and arthroscopic surgery.

There are an estimated 8 to 10 million people worldwide infected with human immunodeficiency virus (HIV). The true extent of infection in the population is unknown, and many are unaware of their HIV status. Arthroscopic and arthroscopically assisted surgery is less invasive and bloody than other orthopaedic procedures, and seemingly less hazardous to surgeons. Nevertheless, the potential for exposure exists. Arthroscopic surgeons routinely experience gown, face-mask and shoe-cover saturation from the splashing of blood-tainted irrigation fluid. Glove perforations by needles, sharps, and bone fragments can occur. Bone and tissue allografts pose risks to both surgeon and patient, as HIV has been recovered from fresh, frozen and freeze-dried specimens. The process of cleaning and disinfecting arthroscopes adequately can damage these expensive devices. This article addresses the safeguards that arthroscopic surgeons should take to prevent exposure to HIV. Effective sterilizing and disinfecting techniques for arthroscopes are also discussed.

The role of arthroscopic debridement after anterior cruciate ligament reconstruction.

This retrospective study included 55 patients who had prior anterior cruciate ligament (ACL) reconstruction; 30 made up the experimental group who had arthroscopic debridement of impinging soft tissue and 25, who did not have a second-look arthroscopy, were used as controls. Impinging tissue was not necessarily the primary reason for arthroscopy in the experimental group. Only nine patients (30%) were debrided solely because of anterior symptoms suggestive of soft tissue impingement; 16 (53%) underwent arthroscopy primarily to assess meniscal repairs; five (17%) were done in conjunction with hardware removal. Both groups were evaluated for pain, crepitation, and anterior laxity at three specific times. Debridement reduced crepitation from 35% to 8% in patients with moderate crepitus, and from 50% to 38% in patients with mild symptoms. The percentage of patients without crepitation increased from 15% to 54% by final follow-up. Predebridement, 14% of patients had moderate pain, and 53% mild pain. By final follow-up, 38% had mild pain and 62% were pain free. Patients benefitted from debridement regardless of method of ACL reconstruction. Arthroscopic debridement did not increase anterior knee translation. Both groups gained extension and had improved activity levels with the passage of time from ACL surgery.

Peripheral meniscal tears: MR findings after conservative treatment or arthroscopic repair.

Follow-up knee magnetic resonance (MR) examinations were performed on 17 patients (18 menisci) with arthroscopically proved tears of the outer third of the meniscus who were treated either conservatively (six patients) or with surgical repair (11 patients). All patients satisfied accepted clinical orthopedic criteria for meniscal healing. MR examinations obtained 3-27 months after injury revealed persistent signal intensity (grade 3), unchanged from that seen on the preoperative study, in all 15 patients in whom both pre- and postoperative studies were obtained and in three of four menisci that were proved to be healed at second-look arthroscopy. It appears that grade 3 signal from both conservatively treated and repaired menisci may persist long after the tear has become asymptomatic and has presumably healed. The presence of such signal should not be interpreted as necessarily indicating meniscal retear in these patients. Persistent signal intensity at the site of previous injuries may account for some reported cases of disagreement between MR and arthroscopic findings.

Arthroscopic debridement of the arthritic knee.

Arthroscopic debridement was carried out in 49 knees of 44 patients. These patients, who had a primary diagnosis of arthritis, were older than 50 years of age. Two-thirds had roentgenographic evidence of severe arthritis. Age, weight, compartment location of arthritis, and presurgical range of motion did not affect surgical results. Symptoms of long duration, arthritic severity as evidenced by roentgenograms, and malalignment predicted poor results. Conversely, shorter duration of symptoms, mechanical symptoms, mild to moderate roentgenographic changes, and crystal deposition correlated with improved results. Surgery offered no benefit for 39% of the patients. Another 9% had temporary improvement, averaging 15 months, but were judged failures at the final follow-up examination. Good or excellent results were achieved in 52% of the patients and maintained through the final follow-up examination in 40% of the patients. Of these, two-thirds had no visible deterioration within a 33-month average follow-up period.

Anatomy and biomechanics of the anterior cruciate ligament.

The ACL is an important living soft-tissue component of ancient origin that acts in combination with other complex structures to provide control of femorotibial kinematics. The effect on the knee of its loss, resulting in disruptive kinematics and often subsequent degenerative changes, probably occurs not only because of its lack of structural integrity but also perhaps because of disruption of its proprioceptive function. The complexity of this ligament and associated normal kinematics of the knee challenges the ability of orthopaedists to devise effective therapeutic measures to reconstitute its function when lost. A clearer understanding of the normal role of the ACL will aid in this effort.

Instrumented testing of functional knee braces.

The ability of seven functional knee braces to control anterior tibial displacement in three severely lax ACL deficient knees using two instrumented testing devices was studied. Some braces were statistically shown to be much better in this regard than others, but not all data obtained was statistically significant. This material should aid one in determining which braces offer the greatest degree of control of anterior tibial displacement in patients with ACL insufficiency.