Desmond Bokor

Variability of measurement of glenoid version on computed tomography scan

The purpose of the study was to determine the variability of measurement that might occur with rotation of the scapula in the coronal plane when computed tomography scanning is used. Ten dry scapula specimens had 4 sets of computed tomography scans performed at +20 degrees, +10 degrees, neutral, and -10 degrees of scapula rotation. The angle of glenoid version was then measured according to the technique of Friedman. The measured value for glenoid version was noted to vary by as much as 10 degrees on the same specimen with minor rotation of the scapula. This result occurred because of differences in the curvature of the vertebral border of the scapula. The measured angle of glenoid version was most likely to vary with rotation of the scapula 10 degrees downward (i.e., glenoid articular surface facing 10 degrees upward). For accurate and reproducible measurement of the glenoid version, it is essential that in the scout view the glenoid orientation is neutral (i.e., glenoid surface is perpendicular to the plane of the computed tomography cut).

Posterior shoulder instability secondary to reverse humeral avulsion of the glenohumeral ligament

BACKGROUND Posterior shoulder instability resulting from a disruption of the posterior capsular structures has been reported. We present the largest series of these injuries in the published literature, propose a definition and highlight the clinical presentation, radiological findings, and associated injuries. MATERIALS AND METHODS A retrospective review of a single shoulder surgeons database was performed identifying posterior instability cases associated with disruption of the posterior capsule. Chart, radiological imaging, and intra-operative findings were reviewed. RESULTS Nineteen patients were identified with an average age lower than the overall posterior instability group. All occurred via a traumatic mechanism, the most common being a forced cross-body adduction. The only consistent symptom was posterior joint line pain. MRI reporting was found to be only 50% sensitive, increased to 78.6% when reviewed by the treating surgeon. Associated injuries are common with 58% having a labral tear, 32% a SLAP lesion, 26% a reverse Bankart lesion, 21% a chondral injury, 21% rotator cuff injury, and 11% extension of the tear into the posterior band of the inferior glenohumeral ligament. DISCUSSION Disruption of the posterior capsule is a rare cause of recurrent posterior instability. There are no specific symptoms that identify the injury, though a mechanism of forced cross-body adduction should raise suspicion. Identification of the injury requires specific attention to the posterior capsule on MRI, preferably performed with the arm in slight external rotation and routine visualization of the posterior capsule via viewing from the anterior portal.

Operative outcome of displaced medial-end clavicle fractures in adults.

The results following nonoperative treatment of displaced, medial end clavicle fractures is often unsatisfactory; but no study has yet reported the outcome of operative fixation of these fractures. This study reports the results of open reduction and internal fixation on displaced, medial end clavicle fractures, in five adult patients (aged 25-52 years, mean 43) including 1 patient with a nonunion. The mean follow-up was 3.3 years (8 months-10.3 years). All fractures had united clinically and radiologically. No complications occurred, and no revision surgery was required. VAS pain scores averaged 0.75 (0-2) at rest, 0.75 (0-2) for normal activities, and 1.0 (0-2) for heavy activities. The mean DASH score was 9.0 (0-17), and all patients were very satisfied with the results of surgery (VAS 10). All patients had a full range of motion of their shoulder at final follow-up and were able to return to pre-injury occupational and activity levels.

The Effect of Humeral Avulsion of the Glenohumeral Ligaments and Humeral Repair Site on Joint Laxity: A Biomechanical Study

PURPOSE The aims of this cadaveric study were to assess the effect of different sizes of humeral avulsion of the glenohumeral ligament (HAGL) lesions on joint laxity and to investigate any difference between repairs with anchors placed in a juxtachondral position and repairs with anchors placed in the humeral neck. METHODS Glenohumeral specimens were tested on a shoulder laxity testing system with translations applied anteriorly up to 30 N, with the joint in 60° of glenohumeral abduction. Testing was conducted in neutral rotation and under 1-Nm external rotation for 5 specimen states: intact, medium HAGL lesion (4:30 to 5:30 clock-face position), large HAGL lesion (3:30 to 6:30 clock-face position), repair with juxtachondral suture anchors, and repair with humeral neck suture anchors. RESULTS Significant increases in translation were observed between the intact and large HAGL lesion states for neutral rotation (1.46 mm [SD, 2.33 mm] at 30 N; P = .049) and external rotation (0.81 mm [SD, 0.72 mm] at 30 N; P = .005). Significant reductions in translation were also observed between the large HAGL lesion and humeral neck repair states for neutral rotation (-1.78 mm [SD, 2.23 mm] at 30 N; P = .022) and external rotation (-0.33 mm [SD, 0.37 mm] at 30 N; P = .015). CONCLUSIONS Large HAGL lesions can increase the passive motion of the glenohumeral joint in both neutral and external rotation, although these differences are small and may be difficult to measure clinically. A repair using anchors placed in the humeral neck is more likely to restore the normal restraint to anterior translation than a juxtachondral repair. CLINICAL RELEVANCE Medium HAGL lesions are unlikely to show significant increases in joint translation, and repair of large HAGL lesions should be achieved with anchors placed in the humeral neck if possible.

Rugby Union on-field position and its relationship to shoulder injury leading to anterior reconstruction for instability

Due to the unique demands of each position on the Rugby Union field, the likelihood of an athlete sustaining a dislocation of their shoulder joint that requires surgical reconstruction may be affected by their position on the field. 166 patients with 184 involved shoulders requiring anterior reconstruction following an on-field Rugby Union injury between January 1996 and September 2008 were analysed. The mean age at time of injury was 18 years with the mean age at time of surgery being 20 years. The most prevalent mechanism of injury was a tackle in 66.3% of players. Players were more likely to suffer injury to their non-dominant shoulder than their dominant side (McNemars Test, p<0.001). Statistical analysis using chi-squared test of goodness of fit showed there was not a uniform risk of injury for all player positions. Positions with significantly different risk of injury were five-eighth (increased risk) and wing (reduced risk). Although we observed an increased risk in flankers and fullbacks, and a lower risk in second row, these results did not reach statistical significance after application of the Bonferroni correction. This information can be utilized by team staff to assist in pre-season conditioning as well as the development of improved muscle co-ordination programmes for the non-dominant shoulder, and planning a graduated return to sport by the player recovering from surgical reconstruction of the shoulder for instability.

Preliminary investigation of a biological augmentation of rotator cuff repairs using a collagen implant: a 2-year MRI follow-up.

BACKGROUND the inability to restore the normal tendon footprint and limit strains on the repair site are thought to contribute to re-tearing following rotator cuff repair. The purpose of this study was to use a collagen implant to augment rotator cuff repairs through the restoration of the native tendon footprint and the induction of new tissue to decrease overall tendon strain. METHODS repairs of full-thickness rotator cuff lesions in 9 adult patients were augmented with a novel collagen implant placed over the bursal surface of the repair. Tendon thickness and footprint anatomy were evaluated using MRI at 3, 6, 12, and 24 months. Clinical results were assessed using standard outcome metrics. Mean follow-up for all patients was 25.8 months. RESULTS the implant induced significant new tissue formation in all patients by 3 months. This tissue matured over time and became indistinguishable from the underlying tendon. At 24 months all repairs remained intact and normal footprint anatomy of the tendon was restored in all patients. All clinical scores improved significantly over time. CONCLUSION the ability of a collagen implant to induce new host tissue formation and restore the normal footprint anatomy may represent a significant advancement in the biological augmentation and ultimate durability of rotator cuff repairs.

Evidence of Healing of Partial-thickness Rotator Cuff Tears Following Arthroscopic Augmentation With a Collagen Implant: A 2-year MRI Follow-up

BACKGROUND partial-thickness rotator cuff tears frequently enlarge due to increased local strain and often progress to full-thickness tears. Studies suggest the addition of new tendinous tissue to injured cuff tendons would significantly decrease peak strain, possibly protecting against tear progression. The aim of this study was to assess the ability of a highly-porous collagen implant to induce new tissue formation and limit tear progression when placed on the bursal surface of partial-thickness cuff tears. METHODS following arthroscopic subacromial decompression, the implant was attached to the bursal surface of the supraspinatus tendon in a prospective series of 13 consecutive patients with intermediate - (3-6 mm) to high-grade (>6 mm) partial - thickness cuff tears (5 articular, 3 bursal, 5 intra-substance). Tendon thickness, defect size, and tendon quality were evaluated using magnetic resonance imaging (MRI) preoperatively and at 3, 6, 12, and 24 months postoperatively. Clinical outcomes were assessed using the Constant and American Shoulder and Elbow Society scores at the same preoperative and follow-up times. All 13 patients completed all follow-up exams (mean length of follow-up 27.0 months, range 23.3-32.0); no patients were lost to follow-up. RESULTS the implant induced significant new tissue formation in all patients by 3 months (mean increase in tendon thickness 2.2 ± 0.26 mm). This tissue matured over time and became radiologically indistinguishable from the underlying tendon. The partial-thickness cuff tears showed consistent filling of the defects, with complete healing in 7 patients at 12 months, and a progressive improvement in tendon quality in the remaining patients. No tear progression was observed by MRI in any of the patients at 24 months. All clinical scores improved significantly over time. At 24 months, 12 of 13 patients (92%) had satisfactory or better results. CONCLUSIONS the results of this clinical study demonstrated the ability of a highly-porous collagen implant to induce new tendon-like tissue formation and create an environment conductive to the healing of partial-thickness cuff tears.

The Effect on Loop Elongation and Stress Relaxation During Longitudinal Loading of FiberWire in Shoulder Arthroscopic Knots

PURPOSE This study examined the viscoelastic properties of 6 common arthroscopic sliding knots (Tennessee slider, Roeder knot, SMC knot, Duncan loop, Weston knot, and Nickys knot) with 3 reversing half-hitches on alternating posts, tied with No. 2 FiberWire (Arthrex, Naples, FL). Knot configuration was designed to simulate a double-row rotator cuff repair with suture bridges. METHODS Constructs were loaded in 20-N increments to 100 N and held for 2 minutes to monitor the viscoelastic behavior in tension. Suture was also tested without tying a knot. RESULTS Stress relaxation increased with loading but did not differ between knot configurations. Initial elongation was highest during the first loading to 20 N. Relaxation was greater for the Roeder knot at 20 N and for the Roeder and SMC knots at 80 N (P < .05) when compared with the loop with no knot. Elongation was greatest for the Roeder knot throughout all loads. This difference was significant at 60 N compared with the knotless loop. At 100 N, all knots showed greater elongation than the knotless loop (P < .05). Testing of suture, without any knots, accounted for more than 75% of the overall stress relaxation and loop elongation of the suture-knot construct. CONCLUSIONS In our in vitro evaluation of the Tennessee slider, Roeder knot, SMC knot, Duncan loop, Weston knot, and Nickys knot in a simulated suture bridge construct, knot configuration was not a variable that influenced elongation or stress relaxation. Overall response was primarily due to the suture itself. With the exception of the Roeder knot, relaxation was similar provided that a secure knot was formed at the time of original tying. CLINICAL RELEVANCE With the evolution of surgical devices, the reliance on knots is decreasing. The results of this study suggest that using knotless techniques for securing the rotator cuff will not change the stress relaxation characteristics of the suture bridge.

A Novel Dynamic Mechanical Testing Technique for Reverse Shoulder Replacements

In vitro mechanical testing of orthopedic implants provides information regarding their mechanical performance under simulated biomechanical conditions. Current in vitro component stability testing methods for reverse shoulder implants are based on anatomical shoulder designs, which do not capture the dynamic nature of these loads. With glenoid component loosening as one of the most prevalent modes of failure in reverse shoulder replacements, it is important to establish a testing protocol with a more realistic loading regime. This paper introduces a novel method of mechanically testing reverse shoulder implants, using more realistic load magnitudes and vectors, than is currently practiced. Using a custom made jig setup within an Instron mechanical testing system, it is possible to simulate the change in magnitude and direction of the joint load during arm abduction. This method is a step towards a more realistic testing protocol for measuring reverse shoulder implant stability.

Mechanical testing of shoulder and elbow implants

Abstract The upper limb undergoes a large range-of-motion (ROM); and therefore, the mechanical testing techniques for the corresponding joint implants need to reflect these movements. The literature shows that aseptic loosening and implant instability are the main shoulder implant related reasons for revision surgery. Aseptic loosening occurs when excessively high stresses lead to degradation of the articular surface of the implant component, resulting in generation of wear debris and implant instability that is mostly caused by eccentric loading. Therefore shoulder implant testing generally falls under two different testing modes: wear testing and stability testing. Both anatomic and reverse type shoulder implants have been tested using a variety of different testing regimes including static and dynamic as well as constant loading, variable loading, and physiological loading. There are currently no standard mechanical testing protocols available for Elbow implants, with only a few reports of varus-valgus laxity test methods found in the literature.