Julien Berhouet

Open Latarjet procedure for management of bone loss in anterior instability of the glenohumeral joint.

Glenoid bone loss is commonly observed in anterior glenohumeral instability and varies greatly in both its extent and significance. In 2000, Burkhart and De Beer reported a recurrence rate of 4% after arthroscopic Bankart repair for anterior instability in patients without significant bone deficiency, whereas the rate of recurrence was 67% in the presence of bony deficiency. They defined significant glenoid bone loss as an ‘‘inverted pear glenoid’’ in which there was greater than 25% loss of the inferior glenoid diameter. In the setting of anterior instability with significant glenoid bone loss, with large Hill-Sachs lesions, or with combined glenoid and humeral bony deficiencies, we have found the Latarjet procedure is effective in restoring stability to the shoulder. In 1954, Latarjet described a coracoid bone block technique to prevent anterior dislocation, suggesting that the horizontal limb of the coracoid process be fixed to the anteroinferior margin of the glenoid with a screw. Augmentation of the anteroinferior glenoid with this procedure has obvious advantages in cases of glenoid bone loss. However, this ‘‘bone blocking effect’’ only partly contributes to the stabilizing mechanism of the Latarjet procedure. Although the precise mechanism is still unknown, the success of the intervention is explained by a triple effect first proposed by Patte:

Evaluation of the role of glenosphere design and humeral component retroversion in avoiding scapular notching during reverse shoulder arthroplasty

BACKGROUNDnScapular notching is a common observation during radiological follow-up of reverse shoulder arthroplasty. The purpose of this study was to evaluate the effect of glenosphere design and humeral component retroversion on movement amplitude in the scapular plane and inferior scapular impingement.nnnMATERIALS AND METHODSnThe Aequalis Reversed Shoulder Prosthesis (Tornier) was implanted into 40 cadaver shoulders. On the glenoid side, 8 different combinations were tested: 36-mm glenosphere: centered (standard), eccentric, with an inferior tilt, or with the center of rotation (COR) lateralized by 5 or 7 mm; and 42-mm centered glenosphere: used alone or with the COR lateralized by 7 or 10 mm. The humeral component was positioned in 0°, 10°, 20°, 30°, and 40° of retroversion. Maximum adduction and abduction were measured when inferior impingement and superior impingement, respectively, were detected.nnnRESULTSnThe average increase in abduction amplitude was 10° and inferior impingement occurred 18° later with a 42-mm glenosphere, especially when it was lateralized by 10 mm, relative to a 36-mm centered glenosphere (P < .05). These 2 combinations provided a 28° increase in the movement amplitude in the scapular plane. Positioning of the humeral component in 10° or 20° of retroversion or in anatomical retroversion was most effective at avoiding inferior impingement but had less effect on abduction range of motion (except with the 42-mm glenosphere).nnnCONCLUSIONnOur study confirmed published results with various glenosphere designs but was unique in describing the effect of humeral retroversion on scapular impingement. Inferior scapular notching can be most effectively prevented by using large-diameter glenospheres with lateralized COR and by making sure to replicate the patients native humeral retroversion.

Rotational positioning of the tibial tray in total knee arthroplasty: A CT evaluation

INTRODUCTIONnVarious surgical techniques have been described to set the rotational alignment of the tibial baseplate during total knee arthroplasty. The self-positioning method (self-adjustment) aligns the tibial implant according to the rotational alignment of the femoral component which is used as a reference after performing repeated knee flexion/extension cycles. Postoperative computed tomography scanning produces accurate measurements of the tibial baseplate rotational alignment with respect to the femoral component.nnnHYPOTHESISnThe rotational positioning of the tibial baseplate matches the rotation of the femoral component with parallel alignment to the prosthetic posterior bicondylar axis.nnnPATIENTS AND METHODSnA 3-month follow-up CT scan was carried out after primary total knee arthroplasty implanted in osteoarthritic patients with a mean 7.8° varus deformity of the knee in 50 cases and a mean 8.7° valgus deformity of the knee in 44 cases. The NexGen LPS Flex (Zimmer) fixed-bearing knee prosthesis was used in all cases. An independant examiner (not part of the operating team) measured different variables: the angle between the anatomic transepicondylar axis and the posterior bicondylar axis of the femoral prosthesis (prosthetic posterior condylar angle), the angle between the posterior bicondylar axis and the posterior marginal axis of the tibial prosthesis, the angle between the posterior marginal axis of the tibial prosthesis and the posterior marginal axis of the tibial bone and finally the angle between the anatomic transepicondylar axis and the posterior marginal axis of the tibial prosthesis.nnnRESULTSnFor the genu varum and genu valgum subgroups, the mean posterior condylar axis of the femoral prosthesis was 3.1° (SD: 1.91; extremes 0° to 17.5°) and 4.7° (SD: 2.7; extremes 0° to 11°) respectively. The tibial baseplate was placed in external rotation with respect to the femoral component: 0.7° (SD : 4.45; extremes -9.5° to 9.8°) and 0.9° (SD: 4.53; extremes -10.8° to 9.5°), but also to the native tibia: 6.1° (SD: 5.85; extremes -4.6° to 22.5°) and 12.5° (SD: 8.6; extremes -10° to 28.9°). The tibial component was placed in internal rotation relative to the anatomic transepicondylar axis: 1.9° (SD : 4.93; extremes -13.6° to 7°) and 3° (SD : 4.38; extremes -16.2° to 4.8°).nnnDISCUSSIONnThe tibial component is aligned parallel to the femoral component whatever the initial frontal deformity (P≅0.7). However, a difference was observed between the rotational alignment of the tibial baseplate and the native tibia depending on the initial deformity and could be attributed to the morphological variations of the bony tibial plateau in case of genu valgum.nnnCONCLUSIONnThe self-positioning method is a reproducible option when using this type of implant since it allows the tibial component to be positioned parallel to the posterior border of the femur.

Dual mobility cup in revision total hip arthroplasty: Dislocation rate and survival after 5 years

BACKGROUNDnDislocation is a common complication of total hip arthroplasty (THA), particularly when performed as revision surgery. Dual mobility cups (DMCs) minimize the risk of instability when implanted during primary THA. However, their usefulness and survival in revision THA remain unclear. We therefore conducted a retrospective study to assess DMC stability and survival at a minimal follow-up period of 5years after revision THA.nnnHYPOTHESISnThe dislocation rate associated with DMCs for revision THA is similar to that seen after primary THA.nnnMATERIALS AND METHODSnCup exchange with implantation of a DMC was performed in 71 patients (74 hips) between 2000 and 2007, for the following reasons: recurrent dislocation (n=22), aseptic loosening (n=38), and infection (n=14). The DMCs were cemented in 47 cases and cementless in 27 cases. The clinical variables (Merle dAubigné-Postel score and Harris Hip Score) and radiological findings were collected retrospectively from the medical records and compared with those obtained at the last follow-up visit.nnnRESULTSnOf the 74 cases, 2 were lost to follow-up. At last follow-up, the mean Merle dAubigné-Postel score was 15.2 (11-18) and the mean Harris Hip Score was 80.4 (51-98). Of the 8 failures, 2 (2/72, 2.7%) were related to mechanical factors (1 case each of aseptic loosening and dislocation) and 6 were changed because of infection (recurrent infection, n=4). Mechanical failure was not linked to a specific reason for revision THA. A radiolucent line was visible in 4 cases but this finding was not associated with clinical manifestations. When failure was defined as cup revision for any non-infectious complication, 5-year implant survival was 99% (95% confidence interval, 93-100%).nnnDISCUSSIONnUse of a DMC in revision THA was associated with a slightly higher dislocation rate (1/72, 1.4%) than in primary THA, whereas 5-year survival was comparable. Cemented DMCs were not associated with a greater risk of loosening.nnnCONCLUSIONnDMCs are useful to decrease the risk of dislocation in revision THA performed for any reason. The low rate of loosening indicates that DMCs do not result in high stresses at the bone-implant interface.nnnLEVEL OF EVIDENCEnIV, retrospective study.

Influence of glenoid component design and humeral component retroversion on internal and external rotation in reverse shoulder arthroplasty: a cadaver study.

BACKGROUNDnA common disadvantage of reverse shoulder arthroplasty is limitation of the range of arm rotation. Several changes to the prosthesis design and implantation technique have been suggested to improve rotation range of motion (ROM).nnnHYPOTHESISnGlenoid component design and degree of humeral component retroversion influence rotation ROM after reverse shoulder arthroplasty.nnnMATERIAL AND METHODSnThe Aequalis Reversed™ shoulder prosthesis (Tornier Inc., Edina, MN, USA) was implanted into 40 cadaver shoulders. Eight glenoid component combinations were tested, five with the 36-mm sphere (centred seating, eccentric seating, inferior tilt, centred with a 5-mm thick lateralised spacer, and centred with a 7-mm thick lateralised spacer) and three with the 42-mm sphere (centred with no spacer or with a 7-mm or 10-mm spacer). Humeral component position was evaluated with 0°, 10°, 20°, 30°, and 40° of retroversion. External and internal rotation ROMs to posterior and anterior impingement on the scapular neck were measured with the arm in 20° of abduction.nnnRESULTSnThe large glenosphere (42 mm) was associated with significantly (P<0.05) greater rotation ROMs, particularly when combined with a lateralised spacer (46° internal and 66° external rotation). Rotation ROMs were smallest with the 36-mm sphere. Greater humeral component retroversion was associated with a decrease in internal rotation and a significant increase (P<0.05) in external rotation. The best balance between rotation ROMs was obtained with the native retroversion, which was estimated at 17.5° on average in this study.nnnDISCUSSIONnOur anatomic study in a large number of cadavers involved a detailed and reproducible experimental protocol. However, we did not evaluate the variability in scapular anatomy. Earlier studies of the influence of technical parameters did not take humeral component retroversion into account. In addition, no previous studies assessed rotation ROMs.nnnCONCLUSIONnRotation ROM should be improved by the use of a large-diameter glenosphere with a spacer to lateralise the centre of rotation of the gleno-humeral joint, as well as by positioning the humeral component at the patients native retroversion value.

Massive rotator cuff tears in patients younger than 65 years. What treatment options are available

Management of massive rotator cuff tears is a therapeutic challenge in patients younger than 65 years, particularly if still working. According to our hypothesis, choice of the most appropriate treatment option mainly depends on the patients functional status and on two predictive factors: height of the subacromial space and fatty muscle infiltration. This is a retrospective, multicenter study of a series of 296 patients younger than 65 years, including 176 males and 120 females with extensive or massive cuff tear. Patients had loss of elevation or external rotation or both in 162 cases. Four types of management of massive rotator cuff tear were performed in this study: anatomical watertight repairs, palliative treatments and partial repairs, watertight repairs using flaps or cuff prostheses and reverse shoulder prostheses. At follow-up, the Constant score (65.6+/-3.4) and active elevation (147.7 degrees +/-32 degrees) had significantly improved. Active external rotation with elbow at the side, and acromiohumeral interval (AHI) were unchanged. Work-related injuries, previous surgeries and complications were correlated with a poorer Constant score. At follow-up, the anatomical repair sub-group had a significantly better Constant score than the three other treatment groups but involved patients with unchanged AHI and a low degree of fatty infiltration of the infraspinatus muscle. The reverse shoulder prostheses sub-group showed better outcomes in terms of function benefits. The presence of a long biceps was correlated with the use of a palliative treatment. In the light of the results and literature, an approach to treatment is suggested related to the functional capacity of patients, the AHI and the degree of fatty infiltration of the infraspinatus and subscapularis muscles.

Meniscus matching: evaluation of direct anatomical, indirect radiographic, and photographic methods in 10 cadaver knees.

INTRODUCTIONnWhen performing meniscus transplantation, allograft size must be carefully matched to the host knee anatomy. The radiographic method devised by Pollard et al. is the current reference standard for meniscus size matching. The primary objective of this study was to compare the accuracy of radiographic measurement according to Pollard, direct anatomic measurement, and photographic measurement.nnnHYPOTHESISnAnatomic and photographic allograft size measurement is as reliable as radiographic host-knee sizing according to Pollard et al.nnnMATERIALS AND METHODSnThree methods for measuring meniscal width and length based on reliable landmarks were assessed in 10 cadaver knees: direct measurement of anatomic specimens, measurement of photographs, and the radiographic method described by Pollard et al.nnnRESULTSnNo significant differences were found between the anatomic and radiographic methods, whereas the anatomic and photographic methods produced significantly different results. Compared to the anatomic method, mean overall measurement error was 7.9% for the radiographic method and 24.1% for the photographic method.nnnDISCUSSIONnThe photographic method used in everyday practice during allograft harvesting is not reliable. Correcting for magnification bias might improve the performance of the photographic method. The radiographic method described by Pollard et al. is acceptable, with a margin of error of about 10%, which is considered tolerable. In practice, however, the radiographic method is burdensome to use.nnnCONCLUSIONnThe best measurement method is direct measurement of the specimen during allograft harvesting.nnnLEVEL OF EVIDENCEnLevel IV.

Effects of the humeral tray component positioning for onlay reverse shoulder arthroplasty design: a biomechanical analysis

BACKGROUNDnRecent shoulder prostheses have introduced a concept of a universal humeral stem component platform that has an onlay humeral tray for the reverse total shoulder arthroplasty (RTSA). No studies have reported how humeral tray positioning can affect the biomechanics of RTSA.nnnMATERIALS AND METHODSnThe Newcastle Shoulder Model was used to investigate the biomechanical effect of humeral tray positioning in the Biomet Comprehensive Total Shoulder System (Biomet, Warsaw, IN, USA) RTSA. Five humeral tray configuration positions were tested: no offset, and 5 mm offset in the anterior, posterior, medial, and lateral positions. Superior and inferior impingement were evaluated for abduction, scapular plane elevation, forward flexion, and external/internal rotation with the elbow at the side (adduction) and at 90° of shoulder abduction. Muscle lengths and moment arms (elevating and rotational) were calculated for the deltoid, the infraspinatus, the teres minor, and the subscapularis.nnnRESULTSnInferior impingement was not affected by the humeral tray position. There was less superior impingement during abduction, scapular plane elevation, and rotation with the shoulder when the tray was placed laterally or posteriorly. The subscapularis rotational moment arm was increased with a posterior offset, whereas infraspinatus and teres minor rotational moment arms were increased with an anterior offset. Very little change was observed for the deltoid elevating moment arm or for its muscle length.nnnCONCLUSIONnPositioning the humeral tray with posterior offset offers a biomechanical advantage for patients needing RTSA by decreasing superior impingement and increasing the internal rotational moment arm of the subscapularis, without creating inferior impingement.

Humeral version in reverse shoulder arthroplasty affects impingement in activities of daily living.

BACKGROUNDnImpingement after reverse shoulder arthroplasty (RSA) has been correlated with implant design and surgical techniques. Previous studies suggested that humeral retroversion can reduce impingement and increase external rotation range of motion (ROM). The purpose of this study was to determine how humeral version affects impingement in activities of daily living (ADLs).nnnMATERIALS AND METHODSnA single surgeon performed virtual RSA on 30 arthritic shoulders that were reconstructed from preoperative computed tomography scans. For each subject, the humeral component was placed into 5 versions: -40°,-20°, 0°, +20°, and +40° (- indicates retroversion,u2009+u2009indicates anteversion). Intra-articular and extra-articular impingement was calculated for 10 ADLs. Impingement-free ROM was also calculated for abduction, forward flexion, scapula plane elevation, and internal/external rotation (standardized tests). Risk of impingement for ADLs was assessed as the collective duration and frequency of impingement across all motions. Frequent impingement sites were identified.nnnRESULTSnFor the ADLs, 0° version showed the least amount of impingement. In contrast, 40° retroversion resulted in the largest ROM for the standardized tests (118°u2009±u200919° abduction, 109°u2009±u200916° forward flexion, 111°u2009±u200910° scapula plane elevation, 140°u2009±u200915° internal/external rotation). The site of impingement changed with version: retroversion increased the extra-articular impingement, and anteversion increased the contact between the inferior glenoid and the humeral cup.nnnCONCLUSIONSnHumeral version can significantly affect impingement in RSA. Maximizing ROM in standardized tests may not reduce the risk of impingement during ADLs. Our results showed that an average 0° of version should be preferred, but the large variability among subjects suggested that optimum version may vary among individuals.

Preoperative planning for accurate glenoid component positioning in reverse shoulder arthroplasty

BACKGROUNDnGlenoid component positioning in reverse shoulder arthroplasty (RSA) is challenging. Patient-specific instrumentation (PSI) has been advocated to improve accuracy, and is based on precise preoperative planning. The purpose of this study was to determine the accuracy of glenoid component positioning when only the glenoid surface is visible, compared to when the entire scapula is visible on a 3D virtual model.nnnMETHODSnCT scans of 30 arthritic shoulders were reconstructed in 3D models. Two surgeons then virtually placed a glenosphere component in the model while visualizing only the glenoid surface, in order to simulate typical intraoperative exposure (blind 3D surgery). One surgeon then placed the component in an ideal position while visualizing the entire scapula (visible 3D surgery). These two positions were then compared, and the accuracy of glenoid component positioning was assessed in terms of correction of native glenoid version and tilt, and avoidance of glenoid vault perforation.nnnRESULTSnMean version and tilt after blind 3D surgery were +1.4° (SD 8.8°) and +7.6° (SD 6°), respectively; glenoid vault perforation occurred in 17 specimens. Mean version and tilt after visible 3D surgery were +0.3° (SD 0.8°) and +0.1° (SD 0.5°), respectively, with glenoid vault perforation in 6 cases. Visible 3D surgery provided significantly better accuracy than blind 3D surgery (P<0.05).nnnCONCLUSIONnWhen the entire scapula is used as reference, accuracy is improved and glenoid vault perforation is less frequent. This type of visualization is only possible with pre-operative 3D CT planning, and may be augmented by PSI.nnnLEVEL OF EVIDENCEnBasic science study. Level III.