The healing effects on the biomechanical properties of joint capsular tissue treated with Ho:YAG laser: An in vivo rabbit study.

PURPOSE: The objective of this study was to evaluate the healing response, after thermal treatment with a Ho:YAG laser, on the biomechanical properties of capsular soft tissue. TYPE OF STUDY: Before and after trial. METHODS: Forty-five New Zealand white rabbits were used in this study. A medial peripatellar retinacular thermal capsuloplasty using a Ho:YAG laser and a lateral peripatellar retinacular release was performed on 1 knee of each rabbit. The contralateral knee served as a control and had a lateral release of the retinaculum only. The temperature of the medial retinaculum was maintained at 55 degrees C +/- 5 degrees C during treatment. The medial peripatellar retinaculum was evaluated at 0, 6, and 12 weeks postoperatively. Tensile testing of the medial retinaculum and a biomechanical assessment evaluating the structural and material properties were performed. RESULTS: The ultimate load (force) of the medial retinaculum was 70%, 56%, and 84% of control at 0, 6, and 12 weeks, respectively, after the procedure. The stiffness (force/deformation) of the medial retinaculum was 83% of control at 0 weeks, 54% at 6 weeks, and 85% at 12 weeks. The ultimate stress (force/area) of the medial retinaculum also showed a significant reduction at 0 and 6 weeks postoperatively, 63% and 62% of control, respectively. By 12 weeks, the ultimate stress was 83% of control. CONCLUSIONS: Thermal treatment of the medial retinaculum with a Ho:YAG laser results in soft tissue with significantly diminished biomechanical properties after treatment. The results of this study suggest that a 12-week period of minimal stress on the capsular tissues should follow a thermal capsuloplasty procedure.

Release of the coracoacromial ligament can lead to glenohumeral laxity: a biomechanical study.

The purpose of this study was to determine change in glenohumeral joint translation after release of the coracoacromial ligament. Six fresh, frozen unpaired glenohumeral joints were tested in a neutral position and at 30 degrees internal and 30 degrees external rotation of the humerus at 0 degrees, 30 degrees, and 60 degrees of abduction on a custom glenohumeral joint translation testing apparatus. A joint compression load of 20 N was simulated; then a 15-N load was applied to the humerus in anterior, posterior, superior, and inferior directions, and translations on the glenoid were measured with an electromagnetic tracking device. The tests were then repeated after a 1.5-cm section of the coracoacromial ligament was released from the acromion. A multivariate analysis of variance was used for statistical analyses with a P value of.05 as the level of significance. At 0 degrees and 30 degrees of abduction, release of the coracoacromial ligament resulted in a significant increase in glenohumeral joint translations, in both the anterior and inferior directions. In addition, the differences in translation between before and after the release of the coracoacromial ligament decreased in all directions as glenohumeral abduction increased, and they were not significant at 60 degrees of abduction in any of the rotations. The results of this study suggest that the coracoacromial ligament has a role in static restraint of the glenohumeral joint. It provides a suspension function and may restrain anterior and inferior translations through an interaction with the coracohumeral ligament. Although this is a biomechanical study without simulation of the shoulder muscles, it indicates that the coracoacromial ligament contributes to glenohumeral stability. Caution should be exercised in the release of the coracoacromial ligament in those with rotator cuff pain associated with glenohumeral instability.

The painful shoulder in the swimming athlete.

Given the popularity of swimming and the high risk of injury associated with the sport, many clinicians come into contact with the swimmer's shoulder. This article describes the mechanism of injury, diagnostic tools, and subtle signs of injury for swimmer's shoulder. It focuses on conservative treatment for the injury, including methods for stretching and strengthening and eliminating acute inflammation.

Glenohumeral translation after arthroscopic thermal capsuloplasty with a radiofrequency probe.

The purpose of this study was to determine whether there are changes in anterior and posterior glenohumeral translation after arthroscopic thermal capsuloplasty with a radiofrequency probe. Anteriorly directed loads of 15 N and 20 N were sequentially applied to the humerus of each of 5 cadaveric glenohumeral joints, and anterior translation on the glenoid was measured through use of a customized translation apparatus and an electromagnetic tracking device. The tests were then repeated with posteriorly directed forces, and posterior translation was measured. During testing, the glenoid was rigidly fixed and the glenohumeral joint was positioned to simulate 90 degrees of shoulder abduction and 90 degrees of external rotation. By means of the radiofrequency probe, thermal energy was then applied to the anteroinferior capsuloligamentous structures; anterior and posterior translation measurements were repeated. The results showed a significant reduction in anterior and posterior translations after thermal capsuloplasty (P < .05). Anterior translation decreased from 6.8 to 4.0 mm (a 41% decrease) with the 15-N load and from 8.6 to 4.9 mm (a 42% decrease) with the 20-N load. Posterior translation decreased from 9.3 to 5.8 mm (a 36% decrease) with the 15-N load and from 10.4 to 6.5 mm (a 35% decrease) with the 20-N load. The results of this study indicate that the radiofrequency probe can be used to decrease both anterior and posterior glenohumeral translation in vitro. The biological effect on heat-treated tissues over time needs to be studied to prove that this is a satisfactory treatment for glenohumeral instability.

Arthroscopic shoulder instability surgery. Complications.

Complications associated with arthroscopic shoulder stabilization are relatively common. Excluding recurrence, complications are rarely disabling. Current statistics undoubtedly underestimate the true incidence of complications. Many complications, including neurovascular injuries and articular damage, are preventable and can be minimized through familiarity with anatomy, proper surgical technique and instrumentation, and clinical experience. Nevertheless, despite these efforts, a few complications, including recurrent instability, persist. Despite careful patient selection and attention to labral pathology and capsular laxity, arthroscopic repairs continue to have success rates lower than those achieved through open means. While cautiously proceeding toward a more complete understanding of the instability continuum, surgeons must maintain a high index of suspicion for new techniques that purport to "solve" the problem of arthroscopic shoulder stabilization, lest the history of enthusiastic but ultimately unsubstantiated claims is repeated. Outcomes must withstand the rigors of scientific scrutiny and the test of time. Without this cautious vigilance, the appeal of today's solutions becomes the fodder of tomorrow's articles about the complications of arthroscopic shoulder stabilization.

The anterior band of the inferior glenohumeral ligament. Assessment of its permanent deformation and the anatomy of its glenoid attachment.

Surgical treatment for traumatic, anterior glenohumeral instability requires repair of the anterior band of the inferior glenohumeral ligament, usually at the site of glenoid insertion, often combined with capsuloligamentous plication. In this study, we determined the mechanical properties of this ligament and the precise anatomy of its insertion into the glenoid in fresh-frozen glenohumeral joints of cadavers. Strength was measured by tensile testing of the glenoid-soft-tissue-humerus (G-ST-H) complex. Two other specimens of the complex were frozen in the position of apprehension, serially sectioned perpendicular to the plane containing the anterior and posterior rims of the glenoid, and stained with Toluidine Blue. On tensile testing, eight G-ST-H complexes failed at the site of the glenoid insertion, representing a Bankart lesion, two at the insertion into the humerus, and two at the midsubstance. For those which failed at the glenoid attachment the mean yield load was 491.0 N and the mean ultimate load, 585.0 N. At the glenoid region, stress at yield was 7.8 +/- 1.3 MPa and stress at failure, 9.2 +/- 1.5 MPa. The permanent deformation, defined as the difference between yield and ultimate deformation, was only 2.3 +/- 0.8 mm. The strain at yield was 13.0 +/- 0.7% and at failure, 15.4 +/- 1.2%; therefore permanent strain was only 2.4 +/- 1.1%. Histological examination showed that there were two attachments of the anterior band of the inferior glenohumeral ligament at the site of the glenoid insertion. In one, poorly organised collagen fibres inserted into the labrum. In the other, dense collagen fibres were attached to the front of the neck of the glenoid.

The anterior band of the inferior glenohumeral ligament: biomechanical properties from tensile testing in the position of apprehension.

The shoulder is the most commonly dislocated joint in the body. The primary restraint to anterior instability is the anterior band of the inferior glenohumeral ligament, where lesions are found after dislocation. The amount of surgical plication required to eliminate instability and maintain full range of shoulder motion remains unclear. We performed tensile testing with the shoulder in abduction and external rotation in 11 human, fresh-frozen, cadaveric glenohumeral joints to improve understanding of the glenoid origin of the anterior band of the inferior glenohumeral ligament and to quantify midsubstance irrecoverable elongation. After measuring the length, width, and thickness of the anterior bands with digital micrometry, biomechanical properties were obtained on bone-ligament-labrum-bone (b-l-l-b) complexes. The complexes were aligned for tensile testing with the humerus abducted 60 degrees and externally rotated. The b-l-l-b complexes were then loaded to failure at a strain rate of 100%/sec. Seven of the complexes failed at the glenoid insertion site (representing the Bankart lesion), 2 at the humeral insertion site, and 2 at the anterior band midsubstance. The ultimate load for the b-l-l-b complexes was 353+/-32 N (mean+/-SE), and tensile stress at failure of the glenoid insertion site averaged 9.6+/-2.1 MPa. When the complex failed at the glenoid insertion site, total elongation of the b-l-l-b complex was 9.1+/-0.5 mm, and the ligament midsubstance strain was 13.0%+/-1.8%. Irrecoverable elongation was only 0.8 mm when failure occurred at the glenoid insertion site. Our results indicate patients with initial anterior glenohumeral instability have small irrecoverable capsuloligamentous elongation so that meaningful plication in addition to repair of the Bankart lesion may be unnecessary.

Reconstruction of the lateral collateral ligament of the knee with patellar tendon allograft. Report of a new technique in combined ligament injuries.

This is a retrospective study of 10 patients with combined cruciate ligament and posterolateral instability who underwent surgical reconstruction between 1991 and 1994. All knees had at least 20 degrees increased external rotation at 30 degrees of knee flexion and from 1+ to 3+ varus instability. Five knees with posterior cruciate ligament ruptures had at least a 2+ Lachman test result. (One knee had both anterior and posterior cruciate ligament injuries). In all cases the lateral collateral ligament was reconstructed with a bone-patellar tendon-bone allograft secured with interference screws. Fixation tunnels were placed in the fibular head and at the isometric point on the femur. The cruciate ligaments were reconstructed with autograft or allograft material. The average follow-up was 28 months. Excessive external rotation at 30 degrees of flexion was corrected in all but one knee. Six patients had no varus laxity, and four patients had 1+ varus laxity at 30 degrees of flexion. The posterior drawer test result decreased, on average, to 1+, and the Lachman test result decreased to between 0 and 1+. The average Tegner score was 4.6, with five patients returning to their preinjury level of activity and four returning to one level lower. These results indicate that this is a promising new procedure for patients with instability resulting from lateral ligament injuries of the knee.

Isometry of the posterior cruciate ligament. Effects of functional load and muscle force application.

The effects of functional load and muscle force application on isometry of the posterior cruciate ligament were determined. Eight fresh-frozen cadaver knees were mounted in a custom-designed rig. A full range of motion and muscle forces were applied through the quadriceps, hamstring, and gastrocnemius tendons during a simulated static squat maneuver. The low-load isometric posterior cruciate ligament point was located 5.63 mm proximal and 0.18 mm anterior to the anatomic center of the posterior cruciate ligament origin on the femur. The high-load state, with no gastrocnemius and hamstring muscle forces applied, shifted the isometric point 6.32 mm proximal and 6.72 mm anterior (P < 0.05). Loading the hamstring and gastrocnemius muscles also shifted the isometric point (P < 0.05). This study indicated that the most isometric region of the posterior cruciate ligament femoral attachment changed significantly when functional loads and muscle forces were applied to the knee. This finding may have implications for both surgical reconstruction and rehabilitation of the posterior cruciate ligament-injured knee.

Glenohumeral joint translation after arthroscopic, nonablative, thermal capsuloplasty with a laser.

The purpose of this study was to determine whether there are changes in anterior and posterior glenohumeral translation after arthroscopic, nonablative, thermal capsuloplasty with a laser. Two anteriorly and two posteriorly directed loads were sequentially applied to the humerus of nine cadaveric glenohumeral joints, and anterior and posterior translation of the humerus on the glenoid was measured. The glenoid was rigidly fixed, and the glenohumeral joint was positioned simulating 90 degrees of shoulder abduction and 90 degrees of external rotation. Using the holmium:yttrium-aluminum-garnet laser, thermal energy was then applied to the anterior capsuloligamentous structures and anterior and posterior translation measurements were then repeated. The results showed a significant reduction in anterior and posterior translation after laser anterior capsuloplasty. Anterior translation decreased from 10.9 +/- 2.0 mm (mean +/- SEM) to 6.4 +/- 1.5 mm with the 15-N load; and from 13.4 +/- 2.1 mm to 8.9 +/- 1.8 mm with the 20-N load. Posterior translation decreased from 7.2 +/- 1.2 mm to 4.4 +/- 0.6 mm with the 15-N load and from 10.4 +/- 1.4 mm to 6.5 +/- 0.9 mm with the 20-N load. These results indicate that the holmium:yttrium-aluminum-garnet laser can be used to decrease glenohumeral joint translation and may be an effective treatment for glenohumeral joint instability.

Shoulder reaction time and muscle-firing patterns in response to an anterior translation force.

The primary restraint preventing humeral head translation is the capsuloligamentous system. Muscle forces can also decrease translation; however, the timing and magnitude of muscle response has not been previously reported. Fine wire electromyographic analysis of the biceps long head, anterior deltoid, pectoralis major, latissimus dorsi, and rotator cuff muscles was performed after an anterior translation force was applied to 15 normal shoulders. The reflex response time (time to 5% maximal muscle test), the protection response time (time to 20% maximal muscle test), the duration of the protection response, and the magnitude of the protection response were calculated. The shoulder reaction data showed 2 consistent patterns. Activation of the anteriorly located muscles preceded the posteriorly located muscles, and the rotator cuff muscles fired with greater magnitude than the more peripherally located muscles.

Evaluation of a proprioception pathway in patients with stable and unstable shoulders with somatosensory cortical evoked potentials.

Histologic studies have documented the presence of mechanoreceptors in the glenohumeral ligaments, capsule, and labrum; however, direct evidence of an intact afferent electrical pathway originating in structures in the shoulder is lacking. Because somatosensory cortical evoked potentials are transmitted by way of the dorsal columns of the spinal cord and carry proprioceptive information, this technique can be easily applied to evaluate the potential proprioceptive function of various intraarticular structures for shoulder stability. Patients have somatosensory cortical evoked potentials monitored while undergoing shoulder arthroscopy. The inferior glenohumeral ligament, middle glenohumeral ligament, subscapularis tendon, biceps tendon, supraspinatus rotator cuff capsule, glenoid labrum, and humeral head were evaluated. The intraarticular structures were stimulated with a monopolar electrode probe inserted through the anterior portal, and the evoked potentials were recorded with scalp electrodes. Generated wave forms were recorded and evaluated by measuring the peak-to-peak amplitude and latency. Three groups of patients with shoulder complications were studied: (1) no intraarticular pathologic condition and stable, (2) anterior instability with a Bankart lesion, and (3) anterior instability with a loose capsule. The articular cartilage of the humeral head generated no wave form in any subject. All other intraarticular structures generated consistent wave forms. No statistically significant difference was seen among the three groups when both amplitude and latency for the intraarticular structures were compared.

Strain of the anterior band of the inferior glenohumeral ligament during capsule failure.

Efficacious surgical treatment of glenohumeral instability requires a combination of anterior band origin repair and capsuloligamentous plication. The purpose of this article was to determine anterior band of the inferior glenohumeral ligament stretching at the time of glenohumeral failure. Thirteen fresh-frozen cadaver glenohumeral joints were thawed and dissected of soft tissue except for the capsuloligamentous structures. Testing was performed with a material testing system device, simulating the anterior instability apprehension position of the shoulder with 90 degrees of shoulder abduction and the humerus externally rotated until the bicipital groove was aligned with the supraglenoid tubercle. The length of each anterior band of the inferior glenohumeral ligament was obtained, and a variable reluctance transducer was applied to the anterior band midsubstance. Tensile testing at a strain rate of 100%/sec ensued until complete capsular failure occurred. Mid-substance strain of the anterior band of the inferior glenohumeral ligament at the time of capsular failure averaged 7.23% +/- 2.25% (mean +/- SD) with a range of 3.68% to 10.68%. Load to failure was 712.9 +/- 238.2 N (range 363.6 to 1136.9 N). All of the glenohumeral capsules failed at the glenoid origin, simulating a Bankart lesion, except for one that failed at the humeral insertion. When the intact capsuloligamentous tissue of the glenohumeral joint is tensile-tested in the apprehension position, there is only slight anterior band strain and failure occurring, predominantly at the glenoid insertion site. This has implications for the success of surgical procedures designed for acute repair of Bankart lesions.

Anterior-inferior (5 o'clock) portal for shoulder arthroscopy.

The present study describes an anterior-inferior portal for arthroscopic shoulder instrumentation at the 5 o'clock position along the glenoid rim. An anterior-inferior portal was established in 14 cadaver shoulders. The portal was created in an inside-to-outside fashion, with the humerus maximally adducted, directing the guide rod as far lateral as possible. Using the described technique, a 5 o'clock portal travels through the subscapularis and lateral to the conjoined tendon. Distance between the portal and the musculocutaneous nerve was 22.9 +/- 4.9 mm (mean +/- SD), and 24.4 +/- 5.7 mm between the portal and the axillary nerve. Previously described portals were either at, or above the 3 o'clock position, resulting in an acute, difficult angle of approach to the glenoid neck. Through a combination of proper arm positioning and rod insertion technique, the 5 o'clock portal can be created safely and is of great potential utility for arthroscopic shoulder stabilization procedures.

The pullout strength and use of tibial interference screws during endoscopic ACL reconstruction surgery.

This article retrospectively reviews the last 89 ACL reconstructions done over the past 24 months by the senior author and also investigates the pullout strength of a 15-mm long interference screw in cadaveric knees. Results revealed that interference screw fixation at the tibial tunnel during endoscopic ACL reconstruction should almost always be possible by ensuring a tibial tunnel with adequate length, taking additional bone on the graft from the proximal tibia, twisting the graft, and possibly using a 15-mm interference screw.

Infraspinatus muscle-splitting incision in posterior shoulder surgery. An anatomic and electromyographic study.

Standard posterior shoulder surgical approaches include infraspinatus tendon detachment and infraspinatus-teres minor interval development. Cadaveric and clinical investigation of a new infraspinatus-splitting approach to the posterior glenohumeral joint was undertaken to assess efficacy in providing exposure, preserving tendon attachment, and avoiding neurologic compromise. Infraspinatus musculotendinous and neural anatomy was examined in 20 cadavers. Four patients with posterior shoulder instability underwent posterior capsulorrhaphy through this infraspinatus-splitting approach, followed by electrodiagnostic testing. Infraspinatus muscle was bipennate in all specimens, the tendinous interval an average 14 mm inferior to the scapular spine at the glenoid rim. The infraspinatus-splitting interval bisected the posterior glenoid rim at its midpoint, whereas the infraspinatusteres minor interval crossed the glenoid rim's lower quarter. The suprascapular nerve provided sole innervation to the infraspinatus muscle in all specimens, entering the infraspinous fossa at the notch as a single trunk 22 mm medial to the glenoid rim. Minimum branching variability was observed. Electrodiagnostic testing showed no evidence of axonal damage or muscle denervation in either infraspinatus pennate bundle. Limiting infraspinatus-splitting dissection medially to 1.5 cm from the posterior glenoid rim prevents damage to any interval-crossing suprascapular nerve branches. Posterior shoulder surgery through a horizontal, longitudinal infraspinatus tendon-splitting approach provides excellent exposure of posterior capsule, labrum, and glenoid, without requiring tendon detachment or causing neurologic compromise.

The treatment of posterior subluxation in athletes.

Posterior instability in athletes is a diagnostic and therapeutic challenge. Athletes have recurrent posterior subluxations rather than true dislocations, and they have pain rather than instability, which makes the diagnosis difficult. The pathology is usually capsular laxity rather than a true reverse Bankart lesion. There is not one diagnostic test, including computed tomography (CT) arthrogram, magnetic resonance imaging (MRI), or arthroscopy, that will always help with the diagnosis. Most athletes respond to conservative care with an exercise program designed to strengthen the posterior deltoid, the infraspinatus, and the teres minor; but, there is still a select group of athletes that cannot perform their sport after an extensive rehabilitation program. The surgical options for these athletes are varied, and the results in most cases are less than ideal. A posterior capsulorrhaphy was performed to treat this problem. This was initially performed with a staple, but this technique has been abandoned for a suture capsulorrhaphy to avoid staple problems. The 40 athletes treated operatively that had adequate follow-up evaluation reflected a 40% failure rate. Most of the failures were related to ligamentous laxity and unrecognized multidirectional instability not treated at the time of surgery. There may be subtle differences between a patient with posterior subluxation and multidirectional instability; these must be differentiated before operation. Also, the higher the competitive level of athlete, the worse the overall results. The high-level athlete must be informed that even if his or her shoulder is stabilized, the functional results may not allow him or her to continue at the same competitive level.

Patellar tendon length change after anterior cruciate ligament reconstruction using the midthird patellar tendon.

The purpose of this study was to determine if use of the midthird patellar tendon autograft contributes to or causes patellar tendon shortening or patella baja in anterior cruciate ligament reconstruction. Thirty-six patients undergoing arthroscopically assisted midthird patellar tendon autograft anterior cruciate ligament reconstruction were studied prospectively. Intraoperative patellar tendon length changes were measured. Half of the patients had the tendon defect closed and half had it left open (closing peritenon only). Radiographic tendon length changes and patella baja were assessed using Insall-Salvati and Blackburne-Peel ratios measured on 45 degrees lateral knee radiographs using an adjustable polypropylene jig. Bilateral films were obtained preoperatively and at 2 weeks, 3 months, and 6 months postoperatively. No patients demonstrated evidence of patellar tendon shortening greater than the 5.5% measurement error. Tendon defect closure resulted in negligible tendon shortening intraoperatively, averaging 2.28% (1.11 mm). Of the 18 patients whose defects were closed, 5 showed no shortening. The remaining 13 patients had measurable tendon shortening less than 4% (2 mm). No patients developed patella baja.

Electromyographic analysis of the anterior cruciate ligament-deficient knee.

The protective relationship of the human anterior cruciate ligament (ACL) by active contraction of the hamstring musculature has been known and understood by sports orthopedists and physical therapists for many years. Rehabilitation programs for patients with torn ACLs as well as those treated with ligament reconstruction have always stressed hamstring strengthening. Research in this area during the past decade has begun to define the proprioceptive mechanism that governs this relationship as well as the actual recording of dynamic muscle firing patterns in pre- and postoperative subjects. Laboratory studies suggest that altered hamstring activity may help these subjects compensate for a knee that is lax because of ACL damage.

Graft-tunnel mismatch in endoscopic anterior cruciate ligament reconstruction: a new technique of intraarticular measurement and modified graft harvesting.

The purpose of this study was to determine the incidence of bitunnel interference fixation and accurate femoral insertion site targeting using a modified technique of endoscopic anterior cruciate ligament (ACL) reconstruction. Thirty-four consecutive central-third bone-patellar tendon-bone autograft modified endoscopic ACL reconstructions were prospectively studied. A new technique was used intraoperatively to directly measure (a) intraarticular (graft) distance (IAD) and (b) patellar tendon graft length, thereby allowing calculation of optimal tibial tunnel length for each case. Accuracy of guide pin placement through this tibial tunnel into the proposed femoral insertion site was assessed, as was the ability to achieve interference fixation in both tunnels (minimum of 20 mm bone interference fixation within the tibial tunnel). A new technique for patellar tendon-bone harvesting and proximal graft fixation to address graft mismatch is described. The average IAD from tibial origin to femoral ACL insertion measured 26.3 +/- 3.0 mm (range 21-33). The average patellar tendon length (LP) was 48.4 +/- 6.0 mm (range 40-63). The average calculated tibial tunnel length (TT) necessary to achieve bitunnel fixation (TT > or = LP + 20 - IAD) was 42.1 +/- 5.3 mm (range 36-57). Establishment of the calculated tibial tunnel length was achieved in 25 cases (74%) (no graft-tunnel mismatch). Graft-tunnel mismatch, in which the tibial tunnel could not be established to the length calculated necessary to accommodate a minimum of 20 mm of bone graft, occurred in nine cases (26%). Graft-tunnel mismatch occurred more frequently in patients whose patellar lengths were > or = 50 mm (p < 0.005), but was not found to correlate specifically to IAD. Recession of the graft up into the femoral tunnel allowed accommodation of the mismatched graft (bitunnel interference screw fixation) in these nine cases, averaging 22.0 +/- 2.98 mm (range 16-29 mm) of available distal bone block fixation. Tibial tunnel fixation of > or = 20 mm was achieved in 30 patients (88%), 18 mm in two, 17 mm in one, and 16 mm in one. Measurement error resulted in inadequate distal graft accommodation in four patients in whom error averaged 3 mm. Targeting of the femoral insertion site guide pin was achieved without requiring any knee manipulation for all cases. Patellar tendon graft protrusion through the tibial tunnel and potentially suboptimal graft fixation poses a frequent problem during endoscopic ACL reconstruction.(ABSTRACT TRUNCATED AT 400 WORDS)