Gerber, Am J Sports Med 2017 - Muscle Degeneration Associated with Rotator Cuff Tendon Release And/or Denervation in Sheep - Article Summary

Muscle Degeneration Associated with Rotator Cuff Tendon Release And/or Denervation in Sheep

Gerber, Wieser, et al.·Am J Sports Med·2017·32 citations·Basic science

Background

The effect of an additional neurological injury (suprascapular nerve traction injury) to a chronically retracted rotator cuff muscle is incompletely understood and warrants clarification.

Purpose

To investigate the microscopic and macroscopic muscle degeneration patterns caused by tendon release and/or muscle denervation in a sheep rotator cuff model.

Methods

Study Design: Controlled laboratory study.

Infraspinatus muscle biopsy specimens (for histological analysis) were obtained from 18 Swiss alpine sheep before and 16 weeks after release of the infraspinatus tendon (tenotomy [T] group; n = 6), transection of the suprascapular nerve (neurectomy [N] group; n = 6), or tendon release plus nerve transection (tenotomy + neurectomy [T&N] group; n = 6).
Magnetic resonance imaging (MRI) and computed tomography (CT) were used to assess retraction (CT), muscle density (CT), volume (MRI T2), and fat fraction (MRI Dixon).
Stiffness of the infraspinatus was measured with a spring scale.

Results

At 16 weeks postoperatively, the mean infraspinatus muscle volume had decreased significantly more after neurectomy (to 47% ± 7% of the original volume; P = .001) and tenotomy plus neurectomy (48% ± 13%; P = .005) than after tenotomy alone (78% ± 11%).
Conversely, the mean amount of intramuscular fat (CT/MRI Dixon) was not significantly different in the 3 groups (T group: 50% ± 9%; N group: 40% ± 11%; T&N group: 46% ± 10%) after 16 weeks.
The mean myotendinous retraction (CT) was not significantly different in the T and T&N groups (5.8 ± 1.0 cm and 6.4 ± 0.4 cm, respectively; P = .26).
Stiffness was, however, most increased after additional neurectomy.
In contrast to muscle changes after tendon release, denervation of the muscle led to a decrease in the pennation angle of lengthened muscle fibers, with a reduced mean cross-sectional area of pooled muscle fibers, a slow- to fast-type transformation, and an increase in the area percentage of hybrid fibers, leading to overall significantly greater atrophy of the corresponding muscle.

Conclusions

Although it is unclear which experimental group (T or T&N) most accurately reflects the clinical scenario in a given case, these findings provide baseline information for clinical differentiation between muscle changes caused by denervation or rotator cuff tendon lesions.

Clinical Relevance: The findings of this study help to understand how and to which extent a neurological lesion of the supplying suprascapular nerve could influence the pattern of anatomic-physiological muscular changes after rotator cuff tendon tears.

Supplemental

Muscle Degeneration Associated with Rotator Cuff Tendon Release And/or Denervation in Sheep.

Gerber, Wieser, et al.Am J Sports Med201732 citationsBasic science

Landmark

Acetabular Defect Classification and Surgical Reconstruction in Revision Arthroplasty. A 6-Year Follow-Up Evaluation.

Paprosky, Lawrence, et al.J Arthroplasty19941,213 citationsRetrospective cohort

Landmark

Effects of Bracing in Adolescents with Idiopathic Scoliosis.

Weinstein, Dobbs, et al.N Engl J Med20131,160 citationsRCT

Landmark

Adolescent Idiopathic Scoliosis: A New Classification to Determine Extent of Spinal Arthrodesis.

Lenke, Blanke, et al.J Bone Joint Surg Am20011,720 citationsDiagnostic study

Landmark

Problems in the Management of Type III (Severe) Open Fractures: A New Classification of Type III Open Fractures.

Gustilo, Williams, et al.J Trauma19842,361 citationsRetrospective cohort

Landmark

Neer Award 2005: The Grammont Reverse Shoulder Prosthesis: Results in Cuff Tear Arthritis, Fracture Sequelae, and Revision Arthroplasty.

Boileau, Hovorka, et al.J Shoulder Elbow Surg20061,115 citationsProspective cohort

Landmark

A System for the Surgical Staging of Musculoskeletal Sarcoma.

Enneking, Goodman, et al.Clin Orthop Relat Res19802,112 citationsRetrospective cohort

Landmark

Fracture Fixation in the Operative Management of Hip Fractures (FAITH): An International, Multicentre, Randomised Controlled Trial.

Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) InvestigatorsLancet2017310 citationsRCT

Landmark

Fatty Muscle Degeneration in Cuff Ruptures. Pre- and Postoperative Evaluation by CT Scan.

Goutallier, Voisin, et al.Clin Orthop Relat Res19942,669 citationsProspective cohort

Landmark

Dislocations after Total Hip-Replacement Arthroplasties.

Lewinnek, Zimmerman, et al.J Bone Joint Surg Am19782,549 citationsRetrospective cohort

Landmark

Morphologic Study of the Glenoid in Primary Glenohumeral Osteoarthritis.

Walch, Khoury, et al.J Arthroplasty19991,142 citationsRetrospective cohort

Landmark

The Three Column Spine and Its Significance in the Classification of Acute Thoracolumbar Spinal Injuries.

DenisSpine (Phila Pa 1976)19832,566 citationsRetrospective cohort

Landmark

The Reverse Shoulder Prosthesis for Glenohumeral Arthritis Associated with Severe Rotator Cuff Deficiency. A Minimum Two-Year Follow-Up Study of Sixty Patients.

Frankle, Vasey, et al.J Bone Joint Surg Am2005773 citationsRetrospective cohort

Landmark

Randomized Trial of Reamed and Unreamed Intramedullary Nailing of Tibial Shaft Fractures.

Study to Prospectively Evaluate Reamed Intramedullary Nails in Patients with Tibial Fractures Investigators, Walter, et al.J Bone Joint Surg Am2008445 citationsRCT

Landmark

A New Classification of Thoracolumbar Injuries: The Importance of Injury Morphology, the Integrity of the Posterior Ligamentous Complex, and Neurologic Status.

Vaccaro, Oner, et al.Spine (Phila Pa 1976)2005866 citationsConsensus statement

Landmark

A Trial of Wound Irrigation in the Initial Management of Open Fracture Wounds.

FLOW Investigators, Guyatt, et al.N Engl J Med2015347 citationsRCT

Landmark

Curve Progression in Idiopathic Scoliosis.

Weinstein, PonsetiJ Bone Joint Surg Am1983641 citationsRetrospective cohort

Landmark

Traumatic Glenohumeral Bone Defects and Their Relationship to Failure of Arthroscopic Bankart Repairs: Significance of the Inverted-Pear Glenoid and the Humeral Engaging Hill-Sachs Lesion.

Burkhart, De BeerArthroscopy20001,884 citationsCase series

Landmark

The Value of the Tip-Apex Distance in Predicting Failure of Fixation of Peritrochanteric Fractures of the Hip.

Baumgaertner, Keggi, et al.J Bone Joint Surg Am19951,441 citationsRetrospective cohort

Landmark

Transchondral Fractures (Osteochondritis Dissecans) of the Talus.

Berndt, HartyJ Bone Joint Surg Am1959945 citationsBiomechanical study

Landmark

Surgical versus Nonsurgical Therapy for Lumbar Spinal Stenosis.

Weinstein, SPORT Investigators, et al.N Engl J Med20081,207 citationsRCT

Landmark

The Lateral Pillar Classification of Legg-Calvé-Perthes Disease.

Herring, Browne, et al.J Pediatr Orthop1992461 citationsRetrospective cohort

Landmark

Natural History of Asymptomatic Rotator Cuff Tears: A Longitudinal Analysis of Asymptomatic Tears Detected Sonographically.

Yamaguchi, Middleton, et al.J Shoulder Elbow Surg2001498 citationsRetrospective cohort

Landmark

The Rotator Crescent and Rotator Cable: An Anatomic Description of the Shoulder's "Suspension Bridge".

Burkhart, Jolson, et al.Arthroscopy1993469 citationsAnatomic study

Landmark

Posterolateral Rotatory Instability of the Elbow.

O'Driscoll, Morrey, et al.J Bone Joint Surg Am1991997 citationsCase series

Landmark

Preoperative versus Postoperative Radiotherapy in Soft-Tissue Sarcoma of the Limbs: A Randomised Trial.

O'Sullivan, Zee, et al.Lancet20021,587 citationsRCT

Landmark

Nonoperative Treatment Compared with Plate Fixation of Displaced Midshaft Clavicular Fractures. A Multicenter, Randomized Clinical Trial.

Canadian Orthopaedic Trauma SocietyJ Bone Joint Surg Am2007804 citationsRCT

Landmark

Microvasculature of the Human Meniscus.

Arnoczky, WarrenAm J Sports Med19821,227 citationsAnatomic study

Landmark

Metastatic Disease in Long Bones. A Proposed Scoring System for Diagnosing Impending Pathologic Fractures.

MirelsClin Orthop Relat Res19891,222 citationsRetrospective cohort

Landmark

Early versus Delayed Decompression for Traumatic Cervical Spinal Cord Injury: Results of the Surgical Timing in Acute Spinal Cord Injury Study (STASCIS).

Fehlings, Rampersaud, et al.PLoS One20121,200 citationsProspective cohort

Landmark

Three-Dimensional Analysis of the Proximal Part of the Humerus: Relevance to Arthroplasty

Robertson, Yamaguchi, et al.J Bone Joint Surg Am2000255 citationsAnatomic study

Landmark

Impingement Lesions.

NeerClin Orthop Relat Res19831,827 citationsReview article

Landmark

Direct Decompressive Surgical Resection in the Treatment of Spinal Cord Compression Caused by Metastatic Cancer: A Randomised Trial.

Patchell, Young, et al.Lancet20052,356 citationsRCT

Landmark

Injuries Involving the Epiphyseal Plate

Salter, HarrisJ Bone Joint Surg Am19631,737 citationsRetrospective cohort

Landmark

The Disabled Throwing Shoulder: Spectrum of Pathology Part III: The SICK Scapula, Scapular Dyskinesis, the Kinetic Chain, and Rehabilitation.

Burkhart, Kibler, et al.Arthroscopy2003929 citations

Landmark

Cuff-Tear Arthropathy.

Neer, Fukuda, et al.J Bone Joint Surg Am1983774 citationsCase series

Landmark

A System of Staging Musculoskeletal Neoplasms.

EnnekingClin Orthop Relat Res19861,083 citationsReview article

Landmark

Elbow Instability.

O'DriscollActa Orthop Belg199959 citationsReview article

Landmark

Effect of Achilles Tendon Lengthening on Neuropathic Plantar Ulcers: A Randomized Clinical Trial

Mueller, Johnson, et al.J Bone Joint Surg Am2003347 citationsRCT

Landmark

The Management of Acetabular Insufficiency Secondary to Metastatic Malignant Disease

HarringtonJ Bone Joint Surg Am1981303 citationsCase series

Landmark

Acetabular Anatomy and the Transacetabular Fixation of Screws in Total Hip Arthroplasty

Wasielewski, Rubash, et al.J Bone Joint Surg Am1990290 citationsAnatomic study

Landmark

Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes: A Prospective Study.

Hewett, Succop, et al.Am J Sports Med20053,495 citationsProspective cohort

Landmark

Grammont Inverted Total Shoulder Arthroplasty in the Treatment of Glenohumeral Osteoarthritis with Massive Rupture of the Cuff. Results of a Multicentre Study of 80 Shoulders.

Sirveaux, Molé, et al.J Bone Joint Surg Br20041,598 citationsRetrospective cohort

Landmark

Hip Morphology Influences the Pattern of Damage to the Acetabular Cartilage: Femoroacetabular Impingement as a Cause of Early Osteoarthritis of the Hip.

Beck, Ganz, et al.J Bone Joint Surg Br20051,955 citationsRetrospective cohort

Landmark

Operative Treatment in 120 Displaced Intraarticular Calcaneal Fractures. Results Using a Prognostic Computed Tomography Scan Classification.

Sanders, Walling, et al.Clin Orthop Relat Res1993891 citationsProspective cohort

Landmark

Fractures of the Ankle. II. Combined Experimental-Surgical and Experimental-Roentgenologic Investigations.

Lauge-HansenArch Surg1950830 citationsBiomechanical study

Landmark

The Natural History of Legg-Calvé-Perthes Disease.

Stulberg, Wallensten, et al.J Bone Joint Surg Am1981810 citationsRetrospective cohort

Landmark

Reconstruction of the Ulnar Collateral Ligament in Athletes.

Jobe, Lombardo, et al.J Bone Joint Surg Am1986758 citationsCase series

Landmark

Replacement Arthroplasty for Glenohumeral Osteoarthritis.

NeerJ Bone Joint Surg Am1974598 citationsCase series

Landmark

Fractures of the Neck of the Talus.

HawkinsJ Bone Joint Surg Am1970556 citationsRetrospective cohort

Landmark

Arthroplasty of the Hip. A New Operation.

CharnleyLancet1961834 citationsCase series

Landmark

Degenerative Lumbar Spondylolisthesis with Spinal Stenosis. A Prospective Study Comparing Decompression with Decompression and Intertransverse Process Arthrodesis.

Herkowitz, KurzJ Bone Joint Surg Am19911,032 citationsProspective cohort

Landmark

Limits of Movement in the Human Knee. Effect of Sectioning the Posterior Cruciate Ligament and Posterolateral Structures.

Grood, Noyes, et al.J Bone Joint Surg Am1988674 citationsBiomechanical study

Landmark

Congenital Club Foot: The Results of Treatment

Ponseti, SmoleyClin Orthop Relat Res1963218 citationsRetrospective cohort

Landmark

The Outcome and Repair Integrity of Completely Arthroscopically Repaired Large and Massive Rotator Cuff Tears.

Galatz, Yamaguchi, et al.J Bone Joint Surg Am20042,135 citationsCase series

Landmark

Magnetic Resonance Classification of Lumbar Intervertebral Disc Degeneration.

Pfirrmann, Boos, et al.Spine (Phila Pa 1976)20013,960 citationsDiagnostic study

Landmark

Displaced Proximal Humeral Fractures. I. Classification and Evaluation.

NeerJ Bone Joint Surg Am19701,957 citationsRetrospective cohort

Landmark

Arthroscopic Repair of Full-Thickness Tears of the Supraspinatus: Does the Tendon Really Heal?

Boileau, Krishnan, et al.J Bone Joint Surg Am20051,256 citationsProspective cohort

Landmark

Contact between the Glenoid and the Humeral Head in Abduction, External Rotation, and Horizontal Extension: A New Concept of Glenoid Track.

Yamamoto, Okada, et al.J Shoulder Elbow Surg2007743 citationsBiomechanical study

Landmark

The Canadian C-Spine Rule for Radiography in Alert and Stable Trauma Patients.

Stiell, Worthington, et al.JAMA20011,283 citationsProspective cohort

Landmark

The Arterial Vascularization of the Humeral Head. An Anatomical Study.

Gerber, Vinh, et al.J Bone Joint Surg Am1990441 citationsAnatomic study

Landmark

SLAP Lesions of the Shoulder.

Snyder, Friedman, et al.Arthroscopy19901,264 citationsCase series

Landmark

Displaced Proximal Humeral Fractures. II. Treatment of Three-Part and Four-Part Displacement.

NeerJ Bone Joint Surg Am19701,283 citationsRetrospective cohort

Landmark

Functional and Structural Outcome after Arthroscopic Full-Thickness Rotator Cuff Repair: Single-Row versus Dual-Row Fixation

Sugaya, Moriishi, et al.Arthroscopy2005918 citationsRetrospective cohort

Landmark

The Treatment of Soft-Tissue Sarcomas of the Extremities: Prospective Randomized Evaluations of (1) Limb-Sparing Surgery Plus Radiation Therapy Compared with Amputation and (2) the Role of Adjuvant Chemotherapy.

Rosenberg, Wesley, et al.Ann Surg19821,347 citationsRCT

Landmark

Anterior Acromioplasty for the Chronic Impingement Syndrome in the Shoulder. 1972.

NeerJ Bone Joint Surg Am1972536 citationsCase series

Landmark

Abnormal Magnetic-Resonance Scans of the Lumbar Spine in Asymptomatic Subjects. A Prospective Investigation.

Boden, Wiesel, et al.J Bone Joint Surg Am1990668 citationsProspective cohort

Landmark

Hip Arthroscopy versus Best Conservative Care for the Treatment of Femoroacetabular Impingement Syndrome (UK FASHIoN): A Multicentre Randomised Controlled Trial.

Griffin, FASHIoN Study Group, et al.Lancet2018542 citationsRCT

Landmark

The Posterior Stabilized Condylar Prosthesis: A Modification of the Total Condylar Design. Two to Four-Year Clinical Experience.

Insall, Burstein, et al.J Bone Joint Surg Am1982470 citationsRetrospective cohort

Landmark

Ectopic Ossification Following Total Hip Replacement. Incidence and a Method of Classification.

Brooker, Riley, et al.J Bone Joint Surg Am19732,880 citationsRetrospective cohort

Landmark

Factors of Patellar Instability: An Anatomic Radiographic Study.

Dejour, Guier, et al.Knee Surg Sports Traumatol Arthrosc19941,987 citationsCase-control study

Landmark

A Biomechanical Study of Normal Functional Elbow Motion.

Morrey, Chao, et al.J Bone Joint Surg Am19811,380 citationsBiomechanical study

Landmark

The Disabled Throwing Shoulder: Spectrum of Pathology Part I: Pathoanatomy and Biomechanics.

Burkhart, Kibler, et al.Arthroscopy20031,304 citationsReview article

Landmark

Grammont Reverse Prosthesis: Design, Rationale, and Biomechanics.

Boileau, Balg, et al.J Shoulder Elbow Surg20051,232 citationsReview article

Landmark

Fractures of the Acetabulum: Classification and Surgical Approaches for Open Reduction. Preliminary Report.

Judet, Letournel, et al.J Bone Joint Surg Am1964980 citationsCase series

Landmark

Inferior Capsular Shift for Involuntary Inferior and Multidirectional Instability of the Shoulder. A Preliminary Report.

Neer, FosterJ Bone Joint Surg Am1980934 citationsCase series

Landmark

The Impact of Positive Sagittal Balance in Adult Spinal Deformity.

Glassman, Schwab, et al.Spine (Phila Pa 1976)20051,878 citationsRetrospective cohort

Landmark

An Analysis of Outcomes of Reconstruction or Amputation after Leg-Threatening Injuries.

Bosse, Castillo, et al.N Engl J Med2002901 citationsProspective cohort

Landmark

Normal and Abnormal Motion of the Shoulder.

Poppen, WalkerJ Bone Joint Surg Am1976886 citationsCase-control study

Landmark

Posterior C1-C2 Fusion with Polyaxial Screw and Rod Fixation.

Harms, MelcherSpine (Phila Pa 1976)20011,528 citationsCase series

Landmark

A Randomized Trial of Vertebroplasty for Osteoporotic Spinal Fractures.

Kallmes, Jarvik, et al.N Engl J Med20091,422 citationsRCT

Landmark

A Randomized Trial of Vertebroplasty for Painful Osteoporotic Vertebral Fractures.

Buchbinder, Murphy, et al.N Engl J Med20091,416 citationsRCT

Landmark

Validity of a Set of Clinical Criteria to Rule Out Injury to the Cervical Spine in Patients with Blunt Trauma. National Emergency X-Radiography Utilization Study Group.

Hoffman, Zucker, et al.N Engl J Med20001,302 citationsProspective cohort

Landmark

Total Hip Arthroplasty or Hemiarthroplasty for Hip Fracture

HEALTH Investigators, Devereaux, et al.N Engl J Med2019507 citationsRCT

Landmark

A Classification for Congenital Limb Malformations.

SwansonJ Hand Surg Am1976429 citationsReview article

Landmark

Treatment of Grade IV Fracture-Dislocation of the Hip.

PipkinJ Bone Joint Surg Am1957445 citationsCase series

Landmark

Compression-Plate Fixation in Acute Diaphyseal Fractures of the Radius and Ulna

Anderson, Park, et al.J Bone Joint Surg Am1975416 citationsCase series

Landmark

Legg-Calve-Perthes Disease. Part II: Prospective Multicenter Study of the Effect of Treatment on Outcome.

Herring, Browne, et al.J Bone Joint Surg Am2004143 citationsProspective cohort

Landmark

The Role of the Scapula in Athletic Shoulder Function.

KiblerAm J Sports Med19981,240 citationsReview article

Landmark

The SLAC Wrist: Scapholunate Advanced Collapse Pattern of Degenerative Arthritis.

Watson, BalletJ Hand Surg Am19841,138 citationsRetrospective cohort

Landmark

Classification and an Algorithmic Approach to the Reconstruction of Femoral Deficiency in Revision Total Hip Arthroplasty.

Valle, PaproskyJ Bone Joint Surg Am2003199 citationsRetrospective cohort

Landmark

The Tibial Plateau Fracture. The Toronto Experience 1968--1975.

Schatzker, Bruce, et al.Clin Orthop Relat Res19791,029 citationsRetrospective cohort

Landmark

Surgical Dislocation of the Adult Hip a Technique with Full Access to the Femoral Head and Acetabulum without the Risk of Avascular Necrosis.

Ganz, Berlemann, et al.J Bone Joint Surg Br20011,367 citationsCase series

Landmark

Predictors of Humeral Head Ischemia after Intracapsular Fracture of the Proximal Humerus.

Hertel, Leunig, et al.J Shoulder Elbow Surg2004837 citationsProspective cohort

Landmark

Early versus Delayed Stabilization of Femoral Fractures. A Prospective Randomized Study.

Bone, Scheinberg, et al.J Bone Joint Surg Am1989795 citationsRCT

Landmark

Acetabulum Fractures: Classification and Management.

LetournelClin Orthop Relat Res1980715 citationsRetrospective cohort

Landmark

A Novel Classification System for Spinal Instability in Neoplastic Disease: An Evidence-Based Approach and Expert Consensus from the Spine Oncology Study Group.

Fisher, Fourney, et al.Spine (Phila Pa 1976)20101,224 citationsConsensus statement

Landmark

Surgical vs. Nonsurgical Treatment of Adults with Displaced Fractures of the Proximal Humerus: The PROFHER Randomized Clinical Trial.

Rangan, PROFHER Trial Collaborators, et al.JAMA2015540 citationsRCT

Landmark

Lumbar Disc Herniation. A Controlled, Prospective Study with Ten Years of Observation.

WeberSpine (Phila Pa 1976)19831,149 citationsRCT

Landmark

Surgical vs. Nonoperative Treatment for Lumbar Disk Herniation. The Spine Patient Outcomes Research Trial (SPORT): A Randomized Trial

Weinstein, Deyo, et al.JAMA20061,086 citationsRCT

Landmark

Health and Function of Patients with Untreated Idiopathic Scoliosis: A 50-Year Natural History Study.

Weinstein, Ponseti, et al.JAMA2003755 citationsProspective cohort

Muscle Degeneration Associated with Rotator Cuff Tendon Release And/or Denervation in Sheep

Gerber, Wieser, et al.·Am J Sports Med·2017·32 citations·Basic science

DOI·PubMed

Background

The effect of an additional neurological injury (suprascapular nerve traction injury) to a chronically retracted rotator cuff muscle is incompletely understood and warrants clarification.

Purpose

To investigate the microscopic and macroscopic muscle degeneration patterns caused by tendon release and/or muscle denervation in a sheep rotator cuff model.

Methods

Study Design: Controlled laboratory study.

Infraspinatus muscle biopsy specimens (for histological analysis) were obtained from 18 Swiss alpine sheep before and 16 weeks after release of the infraspinatus tendon (tenotomy [T] group; n = 6), transection of the suprascapular nerve (neurectomy [N] group; n = 6), or tendon release plus nerve transection (tenotomy + neurectomy [T&N] group; n = 6).
Magnetic resonance imaging (MRI) and computed tomography (CT) were used to assess retraction (CT), muscle density (CT), volume (MRI T2), and fat fraction (MRI Dixon).
Stiffness of the infraspinatus was measured with a spring scale.

Results

At 16 weeks postoperatively, the mean infraspinatus muscle volume had decreased significantly more after neurectomy (to 47% ± 7% of the original volume; P = .001) and tenotomy plus neurectomy (48% ± 13%; P = .005) than after tenotomy alone (78% ± 11%).
Conversely, the mean amount of intramuscular fat (CT/MRI Dixon) was not significantly different in the 3 groups (T group: 50% ± 9%; N group: 40% ± 11%; T&N group: 46% ± 10%) after 16 weeks.
The mean myotendinous retraction (CT) was not significantly different in the T and T&N groups (5.8 ± 1.0 cm and 6.4 ± 0.4 cm, respectively; P = .26).
Stiffness was, however, most increased after additional neurectomy.
In contrast to muscle changes after tendon release, denervation of the muscle led to a decrease in the pennation angle of lengthened muscle fibers, with a reduced mean cross-sectional area of pooled muscle fibers, a slow- to fast-type transformation, and an increase in the area percentage of hybrid fibers, leading to overall significantly greater atrophy of the corresponding muscle.

Conclusions

Background

The effect of an additional neurological injury (suprascapular nerve traction injury) to a chronically retracted rotator cuff muscle is incompletely understood and warrants clarification.

Purpose

To investigate the microscopic and macroscopic muscle degeneration patterns caused by tendon release and/or muscle denervation in a sheep rotator cuff model.

Methods

Study Design: Controlled laboratory study.

Infraspinatus muscle biopsy specimens (for histological analysis) were obtained from 18 Swiss alpine sheep before and 16 weeks after release of the infraspinatus tendon (tenotomy [T] group; n = 6), transection of the suprascapular nerve (neurectomy [N] group; n = 6), or tendon release plus nerve transection (tenotomy + neurectomy [T&N] group; n = 6).
Magnetic resonance imaging (MRI) and computed tomography (CT) were used to assess retraction (CT), muscle density (CT), volume (MRI T2), and fat fraction (MRI Dixon).
Stiffness of the infraspinatus was measured with a spring scale.

Results

At 16 weeks postoperatively, the mean infraspinatus muscle volume had decreased significantly more after neurectomy (to 47% ± 7% of the original volume; P = .001) and tenotomy plus neurectomy (48% ± 13%; P = .005) than after tenotomy alone (78% ± 11%).
Conversely, the mean amount of intramuscular fat (CT/MRI Dixon) was not significantly different in the 3 groups (T group: 50% ± 9%; N group: 40% ± 11%; T&N group: 46% ± 10%) after 16 weeks.
The mean myotendinous retraction (CT) was not significantly different in the T and T&N groups (5.8 ± 1.0 cm and 6.4 ± 0.4 cm, respectively; P = .26).
Stiffness was, however, most increased after additional neurectomy.
In contrast to muscle changes after tendon release, denervation of the muscle led to a decrease in the pennation angle of lengthened muscle fibers, with a reduced mean cross-sectional area of pooled muscle fibers, a slow- to fast-type transformation, and an increase in the area percentage of hybrid fibers, leading to overall significantly greater atrophy of the corresponding muscle.

Conclusions

Background

The effect of an additional neurological injury (suprascapular nerve traction injury) to a chronically retracted rotator cuff muscle is incompletely understood and warrants clarification.

Purpose

To investigate the microscopic and macroscopic muscle degeneration patterns caused by tendon release and/or muscle denervation in a sheep rotator cuff model.

Methods

Study Design: Controlled laboratory study.

Infraspinatus muscle biopsy specimens (for histological analysis) were obtained from 18 Swiss alpine sheep before and 16 weeks after release of the infraspinatus tendon (tenotomy [T] group; n = 6), transection of the suprascapular nerve (neurectomy [N] group; n = 6), or tendon release plus nerve transection (tenotomy + neurectomy [T&N] group; n = 6).
Magnetic resonance imaging (MRI) and computed tomography (CT) were used to assess retraction (CT), muscle density (CT), volume (MRI T2), and fat fraction (MRI Dixon).
Stiffness of the infraspinatus was measured with a spring scale.

Results

At 16 weeks postoperatively, the mean infraspinatus muscle volume had decreased significantly more after neurectomy (to 47% ± 7% of the original volume; P = .001) and tenotomy plus neurectomy (48% ± 13%; P = .005) than after tenotomy alone (78% ± 11%).
Conversely, the mean amount of intramuscular fat (CT/MRI Dixon) was not significantly different in the 3 groups (T group: 50% ± 9%; N group: 40% ± 11%; T&N group: 46% ± 10%) after 16 weeks.
The mean myotendinous retraction (CT) was not significantly different in the T and T&N groups (5.8 ± 1.0 cm and 6.4 ± 0.4 cm, respectively; P = .26).
Stiffness was, however, most increased after additional neurectomy.
In contrast to muscle changes after tendon release, denervation of the muscle led to a decrease in the pennation angle of lengthened muscle fibers, with a reduced mean cross-sectional area of pooled muscle fibers, a slow- to fast-type transformation, and an increase in the area percentage of hybrid fibers, leading to overall significantly greater atrophy of the corresponding muscle.