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Tuesday, June 6, 2023

The Link Between Kyphosis and Subacromial Impingement Syndrome

Brent Brookbush

Brent Brookbush


By Stefanie DiCarrado DPT, PT, NASM CPT & CES

Edited by Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS

Original Citation: Otoshi, K., Takegami, M., Sekiguchi, M., Onishi, Y., Yamazaki, S., Otani, K., Shishido, H., Shinichi, K., Shinichi, K. (2014). Association between kyphosis and subacromial impingement syndrome: LOHAS study. Journal of Shoulder and Elbow Surgery. 23. e300-e307 ABSTRACT

Kyphosis is excessive flexion within a part of the spine.

Why is this relevant?: Subacromial impingement syndrome (SIS) is a commonly reported shoulder injury. Thoracic hyper-kyphosis can create scapular dyskinesis thereby reducing subacromial space and creating the excessive compression and irritation of subacromial structures that leads to SIS. It may not be enough to correct glenohumeral (GH) and scapulothoracic (ST) impairment alone. This study implies that a thoracic hyper-kyphosis may be related to reduced shoulder elevation and the development of SIS, although thoracic hyper-kyphosis would be a secondary factor contributing to pain and dysfunction.

Study Summary

Study DesignCross Sectional Epidemiology Study
Level of EvidenceLevel III: Evidence from non-experimental descriptive studies
Subject Demographics
  • Age: > 40 yrs
  • Gender: Not provided
  • Characteristics: Residents of Tadami & Minamiaizu (towns located in Fukushima Prefecture, Japan)
  • Inclusion Criteria: Individuals > 40yo who participated in an annual health check up in 2010; SIS determined by + Neer or Hawkins impingement test with pain during shoulder elevation
  • Exclusion Criteria: - SIS signs and symptoms
Outcome Measures
  • Age & Gender of Subjects with SIS
  • Lumbar Kyphosis
    • Rib Pelvic Distance Test (RPDT)
      • Positive if: space between the inferior rib margin and superior pelvic crest < 2 finger width

  • Thoracic Kyphosis
    • Wall-occiput Test (WOT):
      • Position: subject stands with back & heels against wall maintaining their head so that an imaginary line from the corner of the eye to the top of the ear would be parallel to the ground
      • Positive if: subject unable to touch the occiput (back of the head) to the wall

  • Reduced Shoulder Elevation (RSE)
    • Goniometric assessment of shoulder elevation
    • Considered "reduced" if < 150°

  • Overall prevalence
    • SIS: occurred in 83.4% of subjects older than 60, no significant difference in age or gender in those with SIS & those without
    • WOT significantly higher in subjects with SIS (31.6% vs 20%)
    • No significant difference in RPDT between subjects with & without SIS
    • Higher incidence of RSE in subjects with SIS (34.3% v 7.7%)

  • Age & gender adjusted analysis
    • Significant link between positive WOT  & RSE
    • Significant link between positive WOT  & SIS
    • Significant link between positive RDPT & RSE
    • No significant link between positive RPDT & SIS

  • Multivariate analysis
    • Significant link between RSE & SIS only
    • No significant link between kyphosis & SIS

ConclusionsThoracic hyperkyphosis may be the root cause of SIS due to the biomechanical impairment it creates -- excessive scapular anterior tipping and decreased spinal extension -- that it leads to a reduction of subacromial space during shoulder elevation.
Conclusions of the ResearchersThere is a definite link between RSE & SIS; excessive thoracic kyphosis may cause scapular dyskinesis and impaired spinal extension mechanics leading to RSE and playing an indirect role in the development of SIS.

Note the increased anterior tipping of the scapula which reduces subacromial space and increases the risk of SIS.

Review & Commentary:

The strength of this study lies in its large sample size of 2144 subjects and standardized methodology. Researchers analyzed data collected from a larger study called the Locomotive Syndrome and Health Outcome in Aizu Cohort Study (LOHAS). The LOHAS study is an ongoing examination of the links between dysfunction within the locomotive systems and risk of cardiovascular disease, mortality, quality of life, and medical costs; part of the evaluation included shoulder and thoracic assessment. The authors clearly defined each evaluation technique for thoracic kyphosis (WOT test) and lumbar kyphosis (RPDT test) along with the criteria for Subacromial Impingement Syndrome (SIS) & Reduced Shoulder Elevation (RSE); all of which were performed by specially trained orthopedic surgeons.

The authors performed multiple statistical analyses for prevalence, age & gender associations, and for multiple variables. This article will not dive into the complexity of statistical analysis but will instead explain what the statistics indicate according to the researchers. Analysis based upon the prevalence of symptoms found a statistically significant number of subjects with SIS also displayed excessive thoracic kyphosis and those without SIS did not; a statistically higher number of subjects with SIS also displayed RSE. When analyzing data by age & gender characteristics, researchers found a statistically significant number of subjects with SIS and/or RSE also presented with excessive thoracic kyphosis. A multivariate analysis found a significant relationship only between SIS & RSE allowing the authors to conclude that RSE is the main dysfunctional link with SIS. However, they acknowledged thoracic kyphosis is likely the cause of RSE due to scapular dyskinses. Researchers reported 95% confidence intervals (CI) for each outcome variable.

The authors described two ways in which thoracic spine positioning may influence SIS through RSE. The decrease in thoracic extension, due to kyphosis, limits the ability to fully elevate the arm. Current literature dictates full bilateral arm elevation requires approximately 15° of thoracic extension (1,2). Further, a rounded thoracic spine will alter the resting position and movement pattern of the scapula. Commonly, this is seen in scapular anterior tipping with downward rotation which will narrow the subacromial space during arm elevation. These clinical findings are supported by research from Grimsby & Gray (1997) and Gumina et al. (2008).

This study is not without limitations. As described by the authors, the WOT and RPDT are not considered as accurate as the Cobb angle in determining spinal kyphosis. However, they provided previous research in which the reliability of these tests were determined (5,6). The researchers acknowledge the lack of scapular dyskinesis assessment and note future studies should include this as it may help clarify the link between excessive thoracic kyphosis and SIS. Lastly, the authors reminded the reader that correlation does not indicate causation; it is not possible through this study to determine if RSE causes, or results from, SIS. Further limitations may include the WOT as a static assessment does not evaluate thoracic extension during arm elevation, but authors believe it does indicate restriction within the thoracic spine.

Why is this study important?

The study is important because it provides evidence from the largest sample size (at the time of publication) providing a link between spinal position and dysfunction of neighboring joints (GH & ST). Movement impairment is rarely local to a single joint as the body is an interdependent system.

How does it affect practice?

Addressing thoracic spine mobility along with efficient scapular movement may provide the optimal means of correcting and preventing SIS. Research by Baskurt et al. (2011) and Struyf et al. (2013) documented the effectiveness of a scapular rehab program. Studies by Wang et al. (1999) and Boyles et al. (2009) demonstrated how improving thoracic mobility by decreasing excessive thoracic kyphosis can improve shoulder range of motion and decrease pain in those with SIS.

Human movement professionals must assessment global and local movement impairment. To isolate dysfunction at one joint or even adjacent joints would be a disservice to your client and a failure of the professional to understand the interdependence of joints throughout the body.

How does it relate to Brookbush Institute Content?

The authors noted that increased thoracic kyphosis may change the resting position of the scapula into a position of excessive anterior tipping, protraction, and downward rotation which will decrease subacromial space. This is a common model of upper body movement dysfunction. The Brookbush Institute promotes a slightly different view in altered scapula position. If the scapula were in a greater state of protraction, it would lead to a shortened and possibly overactive serratus anterior but this is rarely, if ever, the case clinically. Most people exhibit a lengthened and weakened serratus anterior and previous biomechanical analysis noted the underlying causes of scapular dyskinesis as a decrease in posterior tilt, protraction, and upward rotation (11,12). With further examination of individuals with scapular dyskinesis, excessive anterior tipping and downward rotation may provide the illusion of protraction and/or elevation (as described in the Brookbush Institute's predictive model of Upper Body Dysfunction - (UBD) ).

The position of the scapula is only one part of the equation. An excessively kyphotic thoracic spine would lead to the excessive anterior tipping of the scapula. The Brookbush Institute further describes excessive kyphosis related to a decrease in thoracic mobility and over-activity of the Anterior Oblique Subsystem (AOS) within the model of UBD . Using the overhead squat test as a functional assessment, UBD  is typically noted with the arms "falling" as one squats, thumbs rotating down, scapular elevation, and/or an anterior pelvic tilt. If the person places their hands on their hips (eliminating the influence of the latissimus dorsi ) and displays excesive kyphosis and/or a posterior pelvic tilt when squatting, this could be a sign of a reduction in thoracic spine mobility and the AOS  is considered overactive.

The AOS  is a flexion based system of muscles and fascial connections that has a propensity for overactivity. Over time, this overactivity can lead to adaptive shortening of muscle tissue leading to excessive spinal kyphosis, a reduction in scapular mobility, scapular dyskinesis, and eventually, shoulder pain. It is important to address this imbalance by inhibiting over active muscles or systems (pectoralis minor , levator scapulae, rhomboids , AOS , etc.) and activating under active muscles or systems (serratus anterior , mid/lower trapezius , Posterior Oblique Subsystem -- POS ).

Thoracic Spine Mobilization (Self-administered)

Crucifixion Stretch (Gentle thoracic extension mobilization and pectoralis major and minor stretch)

Open Books - Spine Mobilization

Thoracic Spine Rotations Mobilization, Strengthening and Stabilization Exercise

POS Progression: Static Lunge to Row

POS Progression: Reverse Lunge to Row


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© 2014 Brent Brookbush

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