ABSTRACTS 381

search into heat delivery system such as the laser. Our research demonstrates that menisci can be welded, and that the weld strengths are comparable to suture tech- niques. Future research is required to explore the role of in vivo meniscal welding in an animal model with optimization of welding parameters described in our research. This research was funded by the Arthroscopy Association of North America.

The Accuracy of MRI for Evaluating Meniscal Tears in Previously Operated (Non-Virgin) Knees: A Retrospective Correlation to Arthroscopy. Timo- thy E. Foster, Anthony Schepsis, Dennis Crawford, and Jeff Peterson. Boston, Massachusetts, U.S.A.

Introduction: MRI is consistently reported as greater than 90% accurate, sensitive and specific com- pared with arthroscopy for the diagnosis of meniscal tears in "virgin" knees. To date, no study has specifi- cally addressed the accuracy of MRI to diagnose meniscal injury in a previously surgically altered me- niscus. This study evaluates the accuracy of MRI scans in detecting re-tears of the meniscus versus postsurgi- cal change in previously surgically altered knees.

Methods: A retrospective analysis of 37 menisci in 29 MRI examinations (24 patients, 25 knees) was undertaken. Adult patients (mean age, 37 years; range, 17-64 years.) who had undergone a partial menisec- tomy or meniscal repair, and subsequently sustained an injury to the operative knee with a suspected menis- cal re-tear were evaluated by MRI and arthroscopy. One radiologist, considered to be an orthopedic MRI expert, evaluated all the MRI scans. The radiologist was blinded as to the surgical findings, and was given only the history that the patient had previous knee surgery, and a subsequent reinjury.

Results: The overall rate of accuracy for the MRI was 51% (19/37) with respect to definitive identity or exclusion of a meniscal tear when compared with arthroscopic findings. The accuracy rate for identifying a lateral meniscal tear (LM) was 42%, and a medial meniscal tear (MM) was 56%. The overall sensitivity of the MRI diagnosis was 38% 22% LM, 44% MM). The specificity was 100% for both medial and lateral menisci, as no false positives were observed. Accord- ingly, the positive predictive value (PPV) was 100% (11 true positives), and the negative predictive value (NPV) was 31% overall. These results are in direct contrast to MRI in "vi rg in" knees with a very high accuracy rate and the negative predictive value always higher than positive predictive value.

Conclusion: The MRI evaluation of a "non-virgin"

knee has a low accuracy rate, and a low negative pre- dictive value. The use of MRI to evaluate meniscal re- tears is not recommended, even if the MRI is read by a skilled radiologist or surgeon. Arthroscopy may be more precise and cost effective for evaluation of these problems.

The Thermal Properties of Type I Collagen: The Basic Science of the Laser-Assisted Capsular Shift. George Naseef Timothy E. Foster, Shahram Solhpour, and Bertram Zarins. Boston, Massachusetts, U.S.A.

Introduction: The treatment of patients with gleno- humeral instability secondary to capsular laxity re- mains controversial. Clinical trials are currently in- vestigating the use of the holmium:YAG laser to "shr ink" the anterior and inferior shoulder capsule. We describe the basic science pertaining to collage- nous tissue changes with the application of heat.

Methods: Bovine achilles tendon was study in vitro due to its similarity to the shoulder capsule (type I) collagen. The achilles tendons were heated through a water bath with specific control of temperature and humidity. The tendons began to appear to shrink at approximately 60°C, and continued to shrink until ap- proximately 90°C at which time no further shrinkage occurred. The tendons had a maximal shrinkage of approximately 34% of the original length. The tendons were evaluated with electron microscopy and light mi- croscopy. The type I collagen underwent a phase tran- sition from a highly ordered structure to a random coil and/or an amorphous gel. This structural transition occurred rather abruptly, and is known as melting. When melting occurs the collagen fibers must contract in order to allow the highly ordered crystalline triple helix to proceed to a shorter, less ordered, coiled pro- tein.

Conclusion: The "nonablative" laser energy uti- lized in the capsular shift denatues the type I collagen and creates a phase transition. The collagen does not "shr ink", rather it losses its quaternary and tertiary structure with resultant gel formation. This gel forma- tion can create relative weak areas in the tendon (cap- sule) until bioreplacement occurs. The phase transition is very temperature sensitive, and a reversal of the phase transition is not possible once it has occurred. This requires further research to evaluate the decrease in tensile strength associated with gel formation. Re- search is also required to evaluate the bioreplacement of the tendon in an in vivo model.

Revision Anterior Cruciate Ligament (ACL) Re-

Arthroscopy, Vol 12, No 3, 1996

382 ABSTRACTS

construction after Failed Bone Patella Tendon Bone Reconstruction (BPTB). Brian Day. Vancouver, Brit- ish Columbia, Canada.

Introduction: With the increased numbers of pa- tients who have undergone ACL reconstruction, we increasingly face the problem of treatment choice for those who present after failure of such procedures. The BPTB procedure has been labeled the gold standard, a description which leads to an obvious dilemma in selecting a procedure for revision in these cases.

Methods: Thirty-four patients (21 male, 13 female) who presented with recurrent instability after BPTB reconstruction underwent surgical treatment using an arthroscopically aided hamstring technique. Twenty- four patients in this group had undergone a previous open BPTB reconstruction, and 10 had undergone an arthroscopically aided procedure. Technical errors were identified in the BPTB technique in 29 of the 34 patients. Many of the procedures had been performed by relatively inexperienced surgeons. All patients un- derwent revision surgery using a similar procedure, which included removal of the previous graft and hard- ware, and the use of an arthroscopically aided semite- ndinosus and gracilis technique. Patients were not im- mobilized after surgery and were allowed full weight bearing, early full range of motion, unrestricted quadri- ceps and hamstring exercises, as well as early return to impact and pivoting activities. Patients were as- sessed early and late by clinical and objective criteria, which included Cybex and KT1000 arthrometer stud- ies.

Results: All patients were available for follow up assessment, at an average of 3.6 years (range 3.1-4.7). There were no early or late surgical complications. Thirty-two patients achieved and maintained excellent clinical and objective stability, with side to side KT1000 measurements being maintained at below 3 mm. Two patients had persistent laxity, with side to side measurements being significantly less than prere- vision. Two patients were seen at late follow-up with new ruptures to the opposite ACL.

Conclusions: BPTB reconstruction is prone to tech- nical errors that result in early or late failures. Patients with failed reconstructions can be safely and effec- tively treated using an arthroscopically aided ham- string technique.

Arthroscopic Suture Anchor Repair Versus Open Bankart Repair in the Management of Traumatic Anterior Glenohumeral Instability. Stephen C. We- ber. Sacramento, California, U.S.A.

Introduction: Open instability repairs have re- mained the gold standard for the surgical treatment of traumatic unidirection anterior instability. Arthro- scopic repairs using a variety of transscapular suturing techniques have been attempted; early efforts have proven to be surgeon dependant with failure rates as high as 30% in high-risk patients. In a effort to improve these results, several surgeons have described arthro- scopic suturing techniques using suture anchors to bone. While early small series have shown good re- sults, long-term follow-up is lacking and no compara- tive studies have been done to contrast these newer techniques with traditional open repair. Presented here is the first review comparing arthroscopic suture an- chor repair with traditional open repair.

Method: 132 patients were studied over a 3-year period with a minimum of 2-year follow-up. All pa- tients had traumatic unidirectional instability with Bankart lesions confirmed at surgery. Collision athletes were excluded from the arthroscopic group; otherwise patients selected treatment based on data available re- garding perioperative morbidity and recurrence rates at the time of their preoperative appointment. 92 chose open repair and 40 chose arthroscopic repair. Both groups had diagnostic arthroscopy performed prior to their stabilization procedure.

Results: Operative times were shorter for the arthroscopic group, but not significantly so. There were no significant complications in either group. Periopera- tive morbidity was significantly decreased in the arthroscopic group, with no patients admitted in the arthroscopic group and 75 admitted in the open group (P < .01). Final range of motion was similar in both groups with the exception of a slight but significant increase in external rotation in the arthroscopic group (P < .05). There were two recurrences in the open group (2%) and three in the arthroscopic group (8%) (=1.38, P > .20). Throwing sports were three times more likely to be pursued after arthroscopic repair than after open repair.

Discussion: Operative morbidity is significantly im- proved with arthroscopic suture anchor stabilization over traditional open repair. Patient selection and direct fixation of the anterior capsular tissue to bone appears to significantly improve the results of arthroscopic sta- bilization over trans-scapular suturing techniques, ap- proaching but not equaling recurrence rates of tradi- tional open repair. The trade off of increased recurrence versus ability to pursue throwing sports may be acceptable to the high demand throwing athlete.

Arthroscopy, Vol 12, No 3, 1996