Evolution of the throwing shoulder: why apes don't throw well and how that applies to throwing athletes

BACKGROUND

Humans have unique characteristics making us the only primate that can throw well while most other primates throw predominately underhand with poor speed and accuracy. The purpose of this study is to illuminate the uniquely human characteristics that allow us to throw so well. When treating an injury such as a labral tear or capsule tear, this study hopes the reader can gain a better understanding of the issues that lead to the tear and those that may determine the success of treatment besides the actual repair.

METHODS

In addition to a review of scientific and medical literature, information was obtained from interviews and experience with primate veterinarians, anthropologists, archeologists, and professional baseball players. These sources were used to study the connection between evolutionary throwing activities and current sports medicine issues.

RESULTS

Arm acceleration requires a functional kinetic chain, rapid motor sequences, and the ability to absorb elastic energy in the shoulder. Successful treatment of the throwing shoulder requires awareness of the shoulder's position in the kinetic chain and correction of defects in the ability to execute the kinetic chain. Some problems in the shoulder could reflect regression to a more primitive anatomy or dyskinesis. Return of performance requires regaining the elasticity in the tissues of the shoulder to temporarily store kinetic energy. For example, tissue remodeling after rotator cuff repair continues for months to years; however, the newly formed tissue lacks the same elasticity of the native tendon. This suggests why throwing performance typically does not return for 7 or more months after repair even though there may be structural integrity at 3-4 months.

CONCLUSION

The shoulder has developed uniquely in modern man for the act of throwing. The anatomic deficiencies in primates for throwing provide an illustration of the more subtle changes that a throwing athlete might have that are detrimental to throwing. Nonhuman primates have been unable to demonstrate the kinetic chain sequence for throwing secondary to the lack of neurologic pathways required. Humans are more sophisticated and precise in their movements but lack robusticity in their bone and muscle architecture, seen especially in the human rotator cuff. Successful treatment of a throwing injury requires familiarity with the conditions that cause the injury or affect the rehabilitation process. The return of performance following injury or surgery requires regaining the elasticity in the tissues of the shoulder to temporarily store kinetic energy from the kinetic chain.

Sagittal orientation of coracoclavicular ligament reconstruction affects the stability of surgical repair

BACKGROUND

The variation in the anatomic relationship between the coracoid and the clavicle affects the biomechanical stability of coracoclavicular ligament reconstruction (CCLR).

METHODS

Three-dimensional computed tomography reconstruction of 85 patients was analyzed. Anatomic landmarks were used to derive the coracoclavicular sagittal reconstruction angle (sRA). The lateral concave angle, which indicated the shape of the distal clavicle, and the offsets between the clavicle and coracoid were also measured. To investigate the biomechanical effects of the sRA on CCLR, 7 computed tomography scans with different sRAs were 3D printed. Two reconstructions, a single trans-coracoclavicular tunnel and a looped reconstruction technique, were performed sequentially. Models were cyclically loaded at 70 N in the anterior, posterior, and superior directions.

RESULTS

The mean sRA was 68° ± 9.3° (range, 47°-85°). The superoinferior offset between the clavicle and the coracoid and the lateral concave angle positively correlated with the sRA (r = 0.359 and 0.837, respectively; P ≤ .001), whereas the anteroposterior offset had a negative correlation (r = -0.925; P < .001). The sRA had a negative correlation with the anterior displacement of the clavicle (rho = -0.96; P < .001) and a positive correlation with the posterior displacement for both surgical techniques (rho = 1.0; P < .001).

CONCLUSION

The anatomic orientation of the native coracoclavicular ligaments is highly variable in the sagittal plane. Low sagittal angles can reduce anterior stability, whereas high sagittal angles can reduce posterior stability of CCLR.

Three-Dimensional Zero Echo Time Magnetic Resonance Imaging Versus 3-Dimensional Computed Tomography for Glenoid Bone Assessment

PURPOSE

To evaluate the 3-dimensional (3D) zero echo time (ZTE) magnetic resonance imaging (MRI) technique and compare it with 3D computed tomography (CT) for the assessment of the glenoid bone.

METHODS

ZTE MRI using multiple resolutions and multislice CT were performed in 6 shoulder specimens before and after creation of glenoid defects and in 10 glenohumeral instability patients. Two musculoskeletal radiologists independently generated 3D volume-rendered images of the glenoid en face. Post-processing times and glenoid widths were measured. Inter-modality and inter-rater agreement was assessed.

RESULTS

Intraclass correlation coefficients (ICCs) for inter-modality assessment showed almost perfect agreement for both readers, ranging from 0.949 to 0.991 for the ex vivo study and from 0.955 to 0.987 for the in vivo patients. Excellent interobserver agreement was found for both the ex vivo (ICCs ≥ 0.98) and in vivo (ICCs ≥ 0.92) studies. For the ex vivo study, Bland-Altman analyses for CT versus MRI showed a mean difference of 0.6 to 1 mm at 1.0-mm³ MRI resolution, 0.3 to 0.6 mm at 0.8-mm³ MRI resolution, and 0.3 to 0.6 mm at 0.6-mm³ MRI resolution for both readers. For the in vivo study, Bland-Altman analyses for CT versus MRI showed a mean difference of 0.6 to 0.8 mm at 1.0-mm³ MRI resolution, 0.5 to 0.6 mm at 0.8-mm³ MRI resolution, and 0.4 to 0.8 mm at 0.7-mm³ MRI resolution for both readers. Mean post-processing times to generate 3D images of the glenoid ranged from 32 to 46 seconds for CT and from 33 to 64 seconds for ZTE MRI.

CONCLUSIONS

Three-dimensional ZTE MRI can potentially be considered as a technique to determine glenoid width and can be readily incorporated into the clinical workflow.

LEVEL OF EVIDENCE

Level II, development of diagnostic criteria (consecutive patients with consistently applied reference standard and blinding).

Vertical and Rotational Stiffness of Coracoclavicular Ligament Reconstruction: A Biomechanical Study of 3 Different Techniques

PURPOSE

To compare the biomechanical stability of 3 different coracoclavicular reconstruction techniques under rotational and vertical loading using a cadaveric model.

METHODS

In total, 12 cadaveric shoulders were used for testing. The native state was first tested then followed by 3 different reconstruction configurations using suture tapes and cortical buttons: coracoid loop (CL), single-bundle (SB), and double-bundle (DB). Superior displacement was measured by cycling an inferiorly directed force of 70 N to the scapula. The rotational stiffness of the scapula was determined by cycling the scapula in rotational displacement control between 15° of internal and external rotation. The rotational stiffness of the clavicle was determined by rotating the clavicle around its long axis 20° anteriorly and 30° posteriorly in rotational displacement control. All measurements were captured over 10 cycles at a rate of 200 Hz.

RESULTS

Both the CL and SB techniques demonstrated significantly less internal scapular rotation stiffness. (intact: 19.70 ± 9.07 cNm/deg, CL: 3.70 ± 2.63 cNm/deg, SB:4.30 ± 2.66 cNm/deg, P <.001) External scapular rotation stiffness was significantly decreased in all techniques (intact: 17.70 ± 4.43 cNm/deg, CL: 3.30 ± 1.37 cNm/deg, SB: 4.50 ± 1.56 cNm/deg, DB: 4.67 ± 1.99 cNm/deg, P < .001). The CL and SB reconstructions were significantly less stiff with regards to posterior rotation of the clavicle (intact: 5.60 ± 1.80 cNm/deg, CL: 2.90 ± 1.10 cNm/deg, SB: 1.40 ± 0.65 cNm/deg, P < .001). Anterior rotation stiffness of the clavicle was significantly lower in all of the reconstructions (intact: 6.95 ± 1.90 cNm/deg, CL: 3.08 ± 0.84 cNm/deg, SB: 3.64 ± 0.93 cNm/deg, DB: 4.48 ± 1.21 cNm/deg, P < .001).

CONCLUSIONS

None of the described techniques provided equivalent rotational stability in all planes compared with the native state. DB reconstruction presented stiffness characteristics closest to the native state under cyclic loading during internal scapular and posterior clavicular rotation.

CLINICAL RELEVANCE

Additional procedures such as tendon grafting or acromioclavicular ligament reconstruction may be required to control rotational stability.

Professional Advancement and Performance of Amateur Baseball Players Selected in the Major League Baseball Draft With Previous Anterior Cruciate Ligament Reconstruction

BACKGROUND

The effect that an anterior cruciate ligament injury requiring reconstructive surgery has on the professional advancement and performance of amateur baseball players selected in the Major League Baseball draft is not known. Return to sports after anterior cruciate ligament reconstruction (ACLR) in professional athletes has been shown to be high, but mixed results with regard to performance and return to preinjury level have been demonstrated in other sports.

PURPOSE

To (1) investigate the highest level of professional advancement among Major League Baseball draftees with a history of ACLR before entering the draft, (2) examine how much time these players spent on the disabled list (DL) and determine if it was related to the knee, and (3) compare the batting and pitching performance of these players against healthy matched controls.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Predraft medical records of all players selected in the Major League Baseball draft from 2004 to 2008 were reviewed. Players with a documented anterior cruciate ligament injury treated with ACLR before the draft were included. For each study player, 3 controls were identified. Data were accumulated from the time when players were drafted through the 2015 season. Outcome variables included highest professional level of advancement, DL time, and batting and pitching performance.

RESULTS

Forty draftees with a history of ACLR (22 pitchers, 18 position players) were identified and matched to 120 controls (66 pitchers, 54 position players). The difference in the highest level of professional advancement between the groups was not statistically significant (P = .488). The mean total number of times and the mean total number of days on the DL were similar between the groups (1.83 vs 1.47, P = .297; 121.54 vs 109.62, P = .955); however, the mean number of times on the DL because of a knee injury was significantly different (0.28 vs 0.11, P = .004), as was the mean number of days on the DL because of a knee injury (17.36 vs 7.72, P = .009). Among pitchers, there were no differences in performance. Similarly, there were no differences among position players in batting performance.

CONCLUSION

There was no difference between draftees with a history of ACLR and their controls in terms of advancement from the minor to the major leagues. Additionally, pitching and batting performance were similar. Although the 2 groups spent similar time on the DL, the ACLR group spent more time on the DL because of a knee injury than the control group.

Professional advancement, performance, and injury characteristics of baseball players entering the Major League Baseball draft after treatment for shoulder injuries

BACKGROUND

How shoulder injuries treated before the Major League Baseball (MLB) draft affect the player's performance over their career is unclear. The purpose of this study was to determine whether prior shoulder injuries were associated with a difference in the level of performance and advancement of MLB draftees.

METHODS

Before entering the draft, 119 professional baseball players from 2004 to 2010 were treated for a shoulder injury (73% treated surgically) as an amateur. A 3:1 matched case-control was performed to players without prior shoulder injuries by age, position, round selected, and signing bonus. Follow-up data were collected in 2016, and professional advancement, disabled list time, and in-game performance statistics for pitchers were analyzed and compared.

RESULTS

Players with a prior shoulder injury had a statistically higher chance to be assigned to the disabled list then controls (P = .03), but there was no difference in disabled list time or professional advancement. Pitchers with a prior shoulder injury pitched a statistically lower number of innings per game than controls (P = .04). All other in-game performance statistics were not statistically different. The type of treatment did not have any effect on future performance or advancement.

CONCLUSIONS

Professional baseball players treated for prior shoulder injuries at the amateur level were more likely to sustain future disability than their matched controls, but it did not affect professional advancement.

Feasibility of using an inversion-recovery ultrashort echo time (UTE) sequence for quantification of glenoid bone loss

OBJECTIVE

To utilize the 3D inversion recovery prepared ultrashort echo time with cones readout (IR-UTE-Cones) MRI technique for direct imaging of lamellar bone with comparison to the gold standard of computed tomography (CT).

MATERIALS AND METHODS

CT and MRI was performed on 11 shoulder specimens and three patients. Five specimens had imaging performed before and after glenoid fracture (osteotomy). 2D and 3D volume-rendered CT images were reconstructed and conventional T1-weighted and 3D IR-UTE-Cones MRI techniques were performed. Glenoid widths and defects were independently measured by two readers using the circle method. Measurements were compared with those made from 3D CT datasets. Paired-sample Student's t tests and intraclass correlation coefficients were performed. In addition, 2D CT and 3D IR-UTE-Cones MRI datasets were linearly registered, digitally overlaid, and compared in consensus by these two readers.

RESULTS

Compared with the reference standard (3D CT), glenoid bone diameter measurements made on 2D CT and 3D IR-UTE-Cones were not significantly different for either reader, whereas T1-weighted images underestimated the diameter (mean difference of 0.18 cm, p = 0.003 and 0.16 cm, p = 0.022 for readers 1 and 2, respectively). However, mean margin of error for measuring glenoid bone loss was small for all modalities (range, 1.46-3.92%). All measured ICCs were near perfect. Digitally registered 2D CT and 3D IR-UTE-Cones MRI datasets yielded essentially perfect congruity between the two modalities.

CONCLUSIONS

The 3D IR-UTE-Cones MRI technique selectively visualizes lamellar bone, produces similar contrast to 2D CT imaging, and compares favorably to measurements made using 2D and 3D CT.

Performance and Injury Characteristics of Pitchers Entering the Major League Baseball Draft After Ulnar Collateral Ligament Reconstruction

BACKGROUND

Ulnar collateral ligament (UCL) reconstruction (UCLR) has been studied and shown to be a successful procedure for returning overhead athletes to sport. Many studies of Major League Baseball (MLB) players have shown high levels of return to play with successful statistical performance. No study has followed professional advancement of drafted pitchers who underwent UCLR as amateurs when compared with drafted pitchers who did not undergo the procedure before selection in the MLB draft.

HYPOTHESIS

There would be no difference in professional advancement, statistical performance, or injury rate between the UCLR and control groups.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Thirty-eight pitchers with a UCLR as an amateur and 114 controls were identified in the MLB draft between 2006 and 2010. Highest level of professional baseball achieved was collected from all players, as well as statistical performance metrics including velocity, wins, earned run average (ERA), and walks and hits per inning pitched (WHIP). Additional data on future injuries were analyzed for days on the disabled list (DL), risk of being placed on the DL, and DL assignment for elbow injury.

RESULTS

Thirteen of 38 UCLR pitchers reached the major league level (34.2%) compared with 29 of 114 (25.4%) control pitchers, which was not statically significant (P = .295). The UCLR and control groups were similar for average velocity, peak velocity, innings pitched, games, games started, innings per game, ERA, WHIP, wins, losses, saves, batters faced, and innings pitched per year, as well as hits, runs, home runs allowed, strikeouts, batters walked, and batters struck per inning. The UCLR group had a significantly increased rate of DL assignment when compared with controls (86.8% vs 64.0%; P = .008); however, days on DL (152.8 vs 135.6; P = .723) and DL assignment for elbow injury (45.5% vs 43.8%; P = .877) were similar.

CONCLUSION

There was no difference in the rate of professional advancement among pitchers drafted by the MLB who had undergone UCLR as amateurs compared with controls. Both groups had similar statistical performance. Pitchers in the UCLR group had an increased risk of DL assignment but no increase in the number of days on DL or risk of DL placement for elbow injury.

Long head of the biceps brachii tendon: unenhanced MRI versus direct MR arthrography

OBJECTIVE

We sought to determine the diagnostic accuracy of unenhanced MRI and direct MR arthrography (MRA) for evaluation of the intra-articular long head of the biceps brachii tendon (LHBT) using arthroscopy as the gold standard.

MATERIALS AND METHODS

A retrospective review of patients who underwent shoulder MRI (n = 132) and MRA (n = 67) within 12 months prior to arthroscopy was performed. MR images were independently reviewed by two blinded musculoskeletal radiologists. Routinely recorded arthroscopic photos/videos were reviewed by an orthopedic surgeon. The LHBT was graded as normal, tendinosis, partial thickness tear less or greater than 50%, and complete tear. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for tendinosis and tear detection were calculated.

RESULTS

MRI correctly diagnosed fewer normal LHBTs compared to MRA (39-54% versus 74-84%, respectively; p < 0.005). MRI and MRA did not differ significantly in the diagnosis of tendinosis (18-36% and 15-38%, respectively; p > 0.05) and tears (75-83% and 64-73%, respectively; p > 0.05). For tendinosis, MRI versus MRA showed 18-36% and 15-38% sensitivity, 69-79% and 83-91% specificity, 22-28% and 18-50% PPV, 74-76% and 80-86% NPV, and 61-64% and 70-81% accuracy; respectively. For tears, MRI versus MRA showed 75-83% and 64-73% sensitivity, 73-75% and 82-91% specificity, 66-69% and 41-62% PPV, 82-87% and 92-94% NPV, and 74-78% and 79-88% accuracy; respectively.

CONCLUSIONS

No significant difference was found between unenhanced MRI and direct MRA for the detection of tendinosis and tears of LHBTs.

Pathologists overseas: coordinating volunteer pathology services for 19 years

Pathologists Overseas is a nonprofit organization that has been coordinating the efforts of volunteer pathologists and technologists for 19 years to improve and provide affordable pathology services to underserved patients worldwide. This is accomplished by aiding and establishing pathology laboratories, providing diagnostic pathology services, and training local physicians as pathologists. Projects have been completed or are currently active in Kenya, Eritrea, Madagascar, Ghana, Nepal, Bhutan, Peru, El Salvador, and St Lucia. The main challenge is finding enough volunteers to provide uninterrupted service to maintain a project. Our goal is to build on these experiences and continue to both support existing and establish more pathology laboratories worldwide.

The posterior-medial portal

Repair of the posterior superior labrum usually involves placing an anchor posterior to the biceps attachment through an anterior-superior or Wilmington portal. Access to the posterior-superior labrum can be accomplished by establishing a portal medial to the posterior viewing portal. The initial posterior arthroscopic viewing portal is established slightly lateral to a traditional position to allow viewing of the posterior labrum and maintain separation from the posterior-medial portal. The suture anchor can be placed behind the biceps attachment through an anterior portal. The posterior-medial portal is started approximately 3 cm medial to the viewing portal with an 18-gauge needle. The needle is directed anterolateral into the intra-articular space under arthroscopic visualization to determine the appropriate course of the suture retriever. The needle is replaced with a sharp suture retrieval device. The suture from the anchor is pulled through the labrum to achieve a simple or mattress type repair. The suture is retrieved through the anterior-superior portal by finding it medial to the labrum. The sutures can be tied through the anterior-superior portal. The posterior-medial portal can be safely established with attention to technical considerations.

The sesamoids of the metacarpo-phalangeal joint of the thumb: an anatomical and clinical study

Two unusual cases of injury to the sesamoids of the M.P. joint of the thumb are described. An anatomical dissection of the M.P. volar plate region, including the sesamoids, was undertaken to delineate the details of the sesamoids' relationship to the M.P. joint, flexor tendon, flexor tendon sheath and capsule of the joint. Histological studies were carried out to demonstrate a tendinous extension of the muscles that attach to the sesamoids.

The Sesamoids of the Metacarpo-Phalangeal Joint of the Thumb: An Anatomical and Clinical Study

Two unusual cases of injury to the sesamoids of the M.P. joint of the thumb are described. An anatomical dissection of the M.P. volar plate region, including the sesamoids, was undertaken to delineate the details of the sesamoids’ relationship to the M.P. joint, flexor tendon, flexor tendon sheath and capsule of the joint. Histological studies were carried out to demonstrate a tendinous extension of the muscles that attach to the sesamoids.

Puzzling posterior pigmented pruritic patches

A rarely reported dermatologic condition occurring on the scapular area and characterized by itching and pigmentation is presented herein. Several possible etiologies are considered and a mechanism explaining the possible cause is described.